GIOVANNI SEBASTIANO BAROZZI - personale UniMoRe

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GIOVANNI SEBASTIANO BAROZZI

Professore emerito
Dipartimento di Ingegneria "Enzo Ferrari"

Pubblicazioni

2021 - An integrated approach for the analysis and modeling of road tunnel ventilation. Part I: Continuous measurement of the longitudinal airflow profile [Articolo su rivista]
Levoni, P.; Angeli, D.; Cingi, P.; Barozzi, G. S.; Cipollone, M.
abstract

The knowledge of the flow field inside road tunnels under normal operation, let alone fire conditions, is only approximate and partial. The reason is that while the full three-dimensional, unsteady problem is out of reach of numerical methods, on the other hand accurate measurement of the airflow in road and railway tunnels constitutes an extremely demanding task. The present work, structured as a twofold study, takes up the challenge and proposes an original integrated experimental and numerical approach for the analysis and modeling of flow inside a road tunnel and its ventilation systems, aiming at defining a methodology for the creation of “digital twins” of the system itself, on which advanced ventilation and smoke control strategies can be tested and fine-tuned. In this first part, an innovative experimental facility for the continuous acquisition of the longitudinal velocity profile along the whole length of a road tunnel has been designed and built. The facility consists of a survey rake with five bidirectional vane anemometers, which is mounted on a small electric vehicle that can travel through the tunnel at constant speed. This paper reports the design procedure of the measurement facility, with particular focus on the conception and realization of the vehicle carrying the survey rake. Results of the first experimental campaign carried out under the 11611 meters long Mont Blanc road tunnel are presented to corroborate the validity of the approach adopted and the accuracy of the measurement chain.

2017 - Foam evolution in a processed liquid solution [Relazione in Atti di Convegno]
Salerno, Elisabetta; Levoni, Paolo; Barozzi, Giovanni Sebastiano; Malfatto, Annalisa
abstract

Foam formation in a carbonated solution undergoing pouring and decompression is investigated with the use of high-speed imaging. Operational conditions similar to those encountered in industrial bottling processes are applied to inspect the mechanisms that control the foaming behavior in practical filling applications. The evolution of the foam column during pressure release is analyzed in quantitative terms by extracting the foam thickness from the images. The bubble dynamics inside the solution and the destabilization processes on the foam column are seen to have a paramount effect on the observed foam evolution trend. The contributions to foam formation given by the nuclei entrained in the bulk liquid and by the bubble-generating sites on the container walls are finally distinguished and discussed.

2017 - Notes and experiments on the statics of capillary columns [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; Angeli, Diego; Salerno, Elisabetta
abstract

Experimental results are summarized, concerned with the statics of liquid columns in capillary tubes under non-standard conditions. Three configurations are considered: 1. inclined capillary tubes; 2. capillary effect in the horizontal branch of an L-shaped tube; 3. capillary columns in a vertical tube. The effect of inclination on capillary rise (1.) had already been explored in [1] using water in glass-tubes, and it was found that the vertical rise progressively reduces for increasing the tube inclination. This behavior is now confirmed for n-Hexadecane (C16H34). For L-shaped capillaries (2.), the length of the horizontal branch of the tube occupied by the liquid is detected, as a function of the elevation of the branch itself over the feeding pool. The statics of suspended liquid columns (3.) is investigated for two configurations, namely: i. freely suspended columns, and, ii. edge-ending columns. In the latter case, the evaporation transient is also tracked. Even if the experimental basis is limited, the results are sufficient to highlight some of the peculiar features of the statics of capillary columns under the above conditions. In particular, it is shown that the contact angle hysteresis plays a fundamental role in all the cases considered.

2015 - A fast algorithm for Direct Numerical Simulation of natural convection flows in arbitrarily-shaped periodic domains [Relazione in Atti di Convegno]
Angeli, Diego; Stalio, Enrico; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

A parallel algorithm is presented for the Direct Numerical Simulation of buoyancy-induced flows in open or partially confined periodic domains, containing immersed cylindrical bodies of arbitrary cross-section. The governing equations are discretized by means of the Finite Volume method on Cartesian grids. A semi-implicit scheme is employed for the diffusive terms, which are treated implicitly on the periodic plane and explicitly along the homogeneous direction, while all convective terms are explicit, via the second-order Adams-Bashfort scheme. The contemporary solution of velocity and pressure fields is achieved by means of a projection method. The numerical resolution of the set of linear equations resulting from discretization is carried out by means of efficient and highly parallel direct solvers. Verification and validation of the numerical procedure is reported in the paper, for the case of flow around an array of heated cylindrical rods arranged in a square lattice. Grid independence is assessed in laminar flow conditions, and DNS results in turbulent conditions are presented for two different grids and compared to available literature data, thus confirming the favorable qualities of the method.

2015 - Air entrainment in the primary impact of single drops on a free liquid surface [Relazione in Atti di Convegno]
Salerno, Elisabetta; Levoni, Paolo; Barozzi, Giovanni Sebastiano
abstract

Air-bubble entrainment produced by the impact of water drops on a liquid pool is investigated with the use of high-speed imaging. A wide range of drop volumes and impact velocities is considered to determine how the entrainment mechanisms change with varying the impact conditions. Five different entrainment regimes are distinguished on the basis of the observed flow phenomena. Their characteristic features are described in terms of bubble formation, crater evolution, jetting and secondary drop ejection. A regime map is reconstructed in the Froude-Weber space. Results obtained in the present study show good agreement with the phase diagrams reported in the literature and contribute to complete the scenario of the entrainment regimes. Quantitative data about the size and the residence times of the entrained nuclei are also presented.

2015 - Fluid-dynamic characterisation of the Mont Blanc tunnel by multi-point airflow measurements [Articolo su rivista]
Levoni, Paolo; Angeli, Diego; Stalio, Enrico; Agnani, Elia; Barozzi, Giovanni Sebastiano; Cipollone, M.
abstract

Long road and railway tunnels necessitate of a fine-tuned control of the ventilation system to be activated, for both safety and air quality maintenance reasons. This, in turn, requires that the main fluid-dynamic parameters of the tunnel are known with sufficient accuracy, so that the system behaviour can be predicted with reasonable confidence under standard and emergency operative conditions. As a first step in the modelling of the complex system embodying the 11,611. m long Mont Blanc road tunnel, and its ventilation facilities, a movable 5-point survey rake was designed and built-up, for detecting the distribution of the axial velocity on the tunnel cross-section. Two extensive experimental campaigns were carried out, where the airflow-rates were either measured at different stations along the tunnel length (C1), or at a fixed location, under purely axial main-flow conditions and varying the number of the activated axial fan pairs (C2). A simplified dynamic model of the tunnel was developed, and the airflow data from the experiments were used for the model fine-tuning, additional CFD analyses having provided extra information on concentrated pressure losses connected with air inlet and discharge through the tunnel ends. The Mont Blanc tunnel was finally characterised in terms of friction factors and jet-fans installation efficiency.

2015 - Review on the Influence of Biological Deterioration on the Surface Properties of Building Materials: Organisms, Materials, and Methods [Articolo su rivista]
Ferrari, Chiara; Santunione, Giulia; Libbra, Antonio; Muscio, Alberto; Sgarbi, Elisabetta; Siligardi, Cristina; Barozzi, Giovanni Sebastiano
abstract

A strong attention is recently paid to surface properties of building materials as these allows controlling solar gains of the building envelope and overheating of buildings and urban areas. In this regard, deterioration phenomena due to biological aggression can quickly damage solar-reflecting roof surfaces and thus increase sharply solar gains, discomfort, air-conditioning costs and waterproofing degradation. The same deterioration problem has deleterious effect on cultural heritage, ruining its huge historic and artistic value. This work is aimed at providing an overview on the different organisms that affect the surface of most used building materials, to support the design of new building materials with long-lasting surface properties and to find a way to preserve cultural heritage. Artificial ageing is the long-term aim of this investigation, in which what in nature happens after months or years is compressed in a very short time by forcing the growth of microorganisms through a strict control on the different conditioning factors. Both natural and artificial ageing are eventually outlined in the last part of this work to provide a comprehensive idea of what is necessary to study in a complete way biological ageing protocols on building materials. Several characterization techniques are also introduced to analyse the influence of microorganisms on the surface of different building materials.

2014 - A note on capillary rise in tubes [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Angeli, Diego
abstract

Results are presented from an experiment on capillary rise of water in inclined small-bore (Φ = 1.92 mm) cylindrical tubes. A series of thick-walled tubes with different lengths and taken from the same glass rod was used, and the angle of inclination towards the vertical, α, was varied from 0° to 88°. Results indicate that the capillary rise progressively reduces for increasing α, contrary to Jurin’s law predictions. It is observed further that the meniscus seems not to change in shape while varying the tube orientation. Possible consequences of the above observations on the statics of capillary tubes are commented. In the frame of the discussion, an alternative and more general approach for the derivation of the Jurin’s law is proposed.

2014 - I codici commerciali per la Termofluidodinamica Computazionale [Capitolo/Saggio]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; Levoni, Paolo
abstract

Si affrontano alcune problematiche pratiche connesse all'impiego dei codici CFD commerciali

2014 - Natural convection in asymmetric triangular enclosures heated from below [Relazione in Atti di Convegno]
O. M., Kamiyo; Angeli, Diego; Barozzi, Giovanni Sebastiano; M. W., Collins
abstract

Triangular enclosures are typical configurations of attic spaces found in residential as well as industrial pitched-roof buildings. Natural convection in triangular rooftops has received considerable attention over the years, mainly on right-angled and isosceles enclosures. In this paper, a finite volume CFD package is employed to study the laminar air flow and temperature distribution in asymmetric rooftop-shaped triangular enclosures when heated isothermally from the base wall, for aspect ratios (AR) 0.2 ≤ AR ≤ 1.0, and Rayleigh number (Ra) values 8 × 105 ≤ Ra ≤ 5 × 107. The effects of Rayleigh number and pitch angle on the flow structure and temperature distributions within the enclosure are analysed. Results indicate that, at low pitch angle, the heat transfer between the cold inclined and the hot base walls is very high, resulting in a multi-cellular flow structure. As the pitch angle increases, however, the number of cells reduces, and the total heat transfer rate progressively reduces, even if the Rayleigh number, being based on the enclosure height, rapidly increases. Physical reasons for the above effect are inspected.

2013 - A Revised Approach for One-Dimensional Time-Dependent Heat Conduction in a Slab [Articolo su rivista]
Caffagni, A.; Angeli, Diego; Barozzi, Giovanni Sebastiano; Polidoro, Sergio
abstract

Classical Green’s and Duhamel’s integral formulas are enforced for the solution of one dimensional heat conduction in a slab, under general boundary conditions of the first kind. Two alternative numerical approximations are proposed, both characterized by fast convergent behavior. We first consider caloric functions with arbitrary piecewise continuous boundary conditions, and show that standard solutions based on Fourier series do not converge uniformly on the domain. Here, uniform convergence is achieved by integrations by parts. An alternative approach based on the Laplace transform is also presented, and this is shown to have an excellent convergence rate also when discontinuities are present at the boundaries. In both cases, numerical experiments illustrate the improvement of the convergence rate with respect to standard methods.

2013 - Buoyancy-induced transitional flows around an enclosed horizontal cylinder: an experiment [Articolo su rivista]
Fiscaletti, D.; Angeli, Diego; Tarozzi, L.; Barozzi, Giovanni Sebastiano
abstract

An experiment is performed to detect the onset of time-dependent flow regimes within a water-filled square-sectioned cavity containing a horizontal cylindrical heat source. Data are recorded on the cavity cross-section, where velocity fields and local temperature values are detected using a 2D PIV rig, and thermocouples, respectively. Numerical predictions of the experimental runs are carried out, where the system is modelled as a 2D feature. Results are provided for nine values of the leading parameter, the modified Rayleigh number Raq, ranging from 1.48x10^4 to 1.21 x10^5. The system is witnessed to undergo a transition from steady-state, laminar flow to unsteady oscillatory flow at Raq = 5.88x10^4. Experimental data and numerical predictions are compared and cross-validated. The evolution of the flow throughout the bifurcation is described by velocity and temperature profile plots, 2D field visualizations and Fourier analysis of experimental time series. The influence of the flow regime on the overall heat transfer rate of the system is finally discussed.

2013 - Full scale CFD modeling of the Mont Blanc tunnel ventilation system [Relazione in Atti di Convegno]
Agnani, Elia; Angeli, Diego; I., Spisso; Levoni, Paolo; Stalio, Enrico; Barozzi, Giovanni Sebastiano; M., Cipollone
abstract

A exible and versatile full-scale CFD modeling strategy of the air ow in a road tunnel is described. As applied to the case of the Mont-Blanc tunnel, the model includes the entire tunnel length and main characteristic elements of its hybrid ventilation system, including lateral air intake, longitudinal jet fans and air extraction vents. Each of these elements has been modeled, tested and calibrated independently with the help of experimental data collected on-site. In order to simplify the generation of the computational model, seven elementary modules (each 50 m long) have been singled out and meshed independently; such modules, if properly combined, can represent the whole tunnel or just one of its segments. Automatic mesh manipulation scripts were implemented to combine and merge such modules and generate the whole model, which consist of more than two hundred million cells. The validity of the modeling strategy, when appropriate, is veried by means of steady state simulations performed using data from previous in vivo experimental campaigns. Results demonstrate that the deviation between numerical and experimental data is, in most cases, lower than the measurement error of the experimental procedure.

2013 - PIV experiments on a valve for the handling of liquids [Relazione in Atti di Convegno]
Salerno, Elisabetta; Levoni, Paolo; Angeli, Diego; Barozzi, Giovanni Sebastiano
abstract

Particle Image Velocimetry (PIV) is employed to investigate the flow field inside the dummy of a prototype valve to be used for the industrial dosage of liquids. Velocity fields are reconstructed in three regions of the valve passages and for two values of the flow rate. Distilled water is used as the working fluid. Optical limitations were faced during the setup of the apparatus and a description of the expedients adopted is reported. Time-averaged velocity fields reveal the presence of critical fluid behaviours such as throttling, asymmetric flows and vortex generation. Those effects strongly affect the valve performance. The quality of PIV measurements is verified by comparing the experimental data with the results of RANS-based numerical simulations. Contour maps and velocity profiles obtained with the two methods show a very good agreement, thus demonstrating the reliability of PIV in this specific context. A first attempt was also made to characterize the jet flow at the valve outlet using PIV. It is found that in this case the accuracy of the measurements deteriorates, due to the presence of fluid-dynamic instabilities at the jet surface.

2012 - Analysis of the bifurcating orbits on the route to chaos in confined thermal convection [Relazione in Atti di Convegno]
Angeli, Diego; A., Pagano; Corticelli, Mauro Alessandro; A., Fichera; Barozzi, Giovanni Sebastiano
abstract

Bifurcating thermal convection flows arising from a horizontal cylinder centred in a square-sectioned enclosure are studied numerically, with the aim of achieving a more detailed description of the sequence of transitions leading to the onset of chaos, and obtaining a more precise estimate of the critical values of the main system parameter, the Rayleigh number Ra. Only a value of the geometric aspect ratio A of the system is considered, namely A = 2:5, for which a period-doubling cascade was previously observed. Results give evidence of new and interesting features in the route to chaos, such as a window of quasiperiodic flow and the detection of high-order period orbits.

2012 - Experimental Analysis of Unsteady Natural Convection Around a Horizontal Heater in a Water-Filled Enclosure [Relazione in Atti di Convegno]
D., Fiscaletti; Angeli, Diego; Barozzi, Giovanni Sebastiano
abstract

Particle Image Velocimetry (PIV) measurements are carried out to analyse the buoyancy-induced flows originating from a horizontal heated cylinder enclosed in a square-sectioned cavity, filled with distilled water. A description of the experimental setup is provided, alongside with a discussion of critical issues in the measurement process and thermal conditioning of the system. Repeatability of the tests is assessed in both steady-state and unsteady conditions. Results are provided for four different values of the leading parameter, the modified Rayleigh number Raq, ranging from 1:48 104 to 8:62 104. The system is witnessed to undergo a transition from steady-state, laminar flow to unsteady oscillatory flow. The evolution of the flow throughout the bifurcation is described by velocity profile plots and 2D field visualizations. The suitability of the technique for the analysis of transitional natural convection regimes is confirmed by the quality of the experimental data, and the agreement with comparative numerical computations.

2012 - Numerical analisys of Weakly turbulent mixed convection flows in a horizontal pipe [Relazione in Atti di Convegno]
Errico, Orsola; Angeli, Diego; Barozzi, Giovanni Sebastiano; Stalio, Enrico; Corticelli, Mauro Alessandro
abstract

Weakly turbulent developing flows in a heated horizontal pipe are investigated numerically, focusing on the effects of mixedconvection, and for two different thermal boundary conditions (BCs), the uniform heat flux condition and the uniform walltemperature condition. The Reynolds number, based on the pipe diameter and bulk velocity, is set equal to Re = 5750 and the molecular Prandtl number Pr = 12. For the sake of comparison, the Grashof number values GrH = 3×108 and GrT = 2.3×1010 are chosen for isoflux and isothermal boundary conditions, respectively. Turbulence is modeled by using alternative RANS approaches. Four RANS models are considered, namely the realizable k-e (RKE), the renormalization-group k-e (k-e RNG), the Gibson’s q-z model, and the Shear-Stress Transport k-w model (k-w SST). Results allow to discriminate the performance ofthe different turbulent models and give hint on the effects of the buoyancy induced flow over the leading forced component.The effect of the thermal boundary condition is finally discussed.

2012 - T.A.L.P.A.: an innovative facility for cotinous longitudibnal air flow profile acquisition in tunnels [Relazione in Atti di Convegno]
Levoni, Paolo; A., Scorcioni; Angeli, Diego; Stalio, Enrico; Barozzi, Giovanni Sebastiano; M., Cipollone
abstract

The knowledge of the flow field inside road tunnels under fire conditions and normal operation is only approximate andpartial. The reason is that while the full three-dimensional, unsteady problem is out of reach of numerical methods, on theother hand accurate measurement of the airflow in road and railway tunnels constitutes an extremely challenging task.Aiming at performing easy and accurate in situ measurements of the flow field in road tunnel under different conditions, aninnovative experimental facility for the continuous acquisition of the longitudinal velocity profile has been designed and built.The facility is made up with a survey rake with five bidirectional vane anemometers, which is mounted on a small electricvehicle that can travel through the tunnel at constant speed. This paper reports the design procedure of the measurementfacility, with particular focus on the conception and realization of the vehicle carrying the survey rake. Results of the firstexperimental campaign carried out under the 11611 meters long Mont Blanc road tunnel are also presented to corroborate thevalidity of the approach adopted and the accuracy of the measurement chain.

2011 - Bifurcations of Natural Convection Flows from an Enclosed Cylindrical Heat Source [Articolo su rivista]
Angeli, Diego; A., Pagano; Corticelli, Mauro Alessandro; A., Fichera; Barozzi, Giovanni Sebastiano
abstract

A numerical analysis of transitional natural convection from a confined thermal source is presented. The system considered is an air-filled, square-sectioned 2D enclosure containing a horizontal heated cylinder. The resulting flow is investigated with respect to the variation of the Rayleigh number, for three values of the aspect ratio A. The first bifurcation of the low-Ra fixed-point solution is tracked for each A-value. Chaotic flow features are detailed for the case A = 2.5. The supercritical behaviour of the system is investigated using nonlinear analysis tools and phase-space representations, and the effect of the flow on heat transfer is discussed.

2011 - Concept, design, construction and testing of an experimental facility for multi-point longitudinal air flow measurements in tunnels [Relazione in Atti di Convegno]
Levoni, Paolo; Angeli, Diego; Stalio, Enrico; Barozzi, Giovanni Sebastiano; M., Cipollone
abstract

Performing accurate measurements during a set of fire tests in a road tunnel is a notoriously difficult task to carry out. As in addition the full three-dimensional, unsteady problem is out of reach of numerical methods, the knowledge of the flow field inside road tunnels under fire conditions and also during normal operation is in many cases only approximate and partial. As a consequence, also the influence of road tunnel ventilation on fire development and spread are still not clarified, even for the simple longitudinal ventilation. Aiming at performing easy and accurate in situ measurements of the flow field in road tunnel under different conditions, a portable experimental facility including a survey rake with five bidirectional vane anemometers has been designed and built. This paper reports the design procedure of the measurement facility, all the details of the measurement chain and also results of the first experimental campaign carried out under the 11611 meters long Mont Blanc road tunnel. Unlike data provided by the S.C.A.D.A., a monotonic axial velocity profile resulted, which is theoretically justified in the case of semi-transverse ventilation.

2011 - Elementi di fisica tecnica per l'ingegneria [Traduzione di Libro]
Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano; Muscio, Alberto; Stalio, Enrico; Tartarini, Paolo
abstract

Scopo del testo è introdurre ai principi della termodinamica, della meccanica dei fluidi e della trasmissione del calore attraverso un approccio integrato, assai importante per lo studente ingegnere

2011 - Experimental characterization of a road tunnel jet fan by direct measurement of the velocity components at the inflow and out flow section [Relazione in Atti di Convegno]
Levoni, Paolo; Angeli, Diego; E., Canepa; Barozzi, Giovanni Sebastiano; M., Cipollone
abstract

Axial jet fans installed at the ceiling are worldwide diffuse devices for longitudinal ventilation control in road tunnels underordinary operating conditions and also for smoke control under fire conditions.An experimental characterization of one of the jet fans actually operating inside the tunnel Mont Blanc has been carried out bymeans of a multi-axial hot wire technique. Inflow and outflow instantaneous axial, radial and tangential velocity profiles havebeen measured in still air at the nominal speed of rotation of the fan. Time averaged velocity profiles and turbulent kineticenergy profile have been derived from instantaneous data. In the paper, details of the testing procedure, the experimental setup,the collected data and the post-processed profiles are reported.

2011 - Influence of thermal boundary conditions on the dynamic behaviour of a rectangular single-phase natural circulation loop [Articolo su rivista]
Misale, M.; Garibaldi, P.; Tarozzi, L.; Barozzi, Giovanni Sebastiano
abstract

Natural circulation of distilled water and FC43 has been experimentally investigated in a rectangular loopcharacterized by internal diameter of 30 mm and total length of 4.1 m. The aim of the present study is toanalyse the influence of thermal boundary conditions on the flow regimes inside the pipes and on thestability of the system. The new aspect of the present research is the possibility of tuning the heat sinktemperature in a range between 20 C and +30 C by means of a cryostat. This kind of analysis could beuseful for the design of systems characterized by a wide range of environment temperatures, as for examplefor aerospatial applications. The other parameters investigated were the heat flux transferred to thefluid, which varied between 0.1 kW and 2.5 kW, and the thermo-physical properties of the working fluid.The system showed both stable and unstable behaviour. In particular, in the case of FC43 the loop wasmore unstable and it was characterized by higher velocities and frequencies compared to the case of distilledwater.It was found that the stability threshold could be crossed by varying only the heat sink temperature, demonstrating the importance of this boundary condition on the dynamics of the system. Different flow regimes and fluid velocities were observed. In the case of steady-state flow, Vijayan’s correlation (Vijayan et al., 2000) was tested and found to give good agreement with experimental data. Linear stability analysis was made following the Vijayan’s model. In particular, the effect of heat sink temperature was considered in the dimensionless Stanton number based on the overall heat transfer coefficient at the heat sink. Finally, Ultrasound Pulsed Doppler Velocimeter (UPDV) was used on a natural circulation loop for the first time, and gave a preliminary validation of the traditional fluid velocity measurement method based on the frequency analysis.

2011 - Non-Newtonian and flow pulsatility effects in simulation models of a stented intracranial aneurysm [Articolo su rivista]
Cavazzuti, Marco; Atherton, M. A.; Collins, M. W.; Barozzi, Giovanni Sebastiano
abstract

Three models of different stent designs implanted in a cerebral aneurysm, originating from the virtual intracranial stenting challenge, are meshed and the flow characteristics simulated using commercial computational fluid dynamics (CFD) software in order to investigate the effects of non-Newtonian viscosity and pulsatile flow. Conventional mass inflow and wall shear stress (WSS) output are used as a means of comparing the CFD simulations. In addition, a WSS distribution is presented, which clearly discriminates in favour of the stent design identified byother groups. It is concluded that non-Newtonian and pulsatile effects are important to include in order to avoid underestimating WSS, understand dynamic flow effects, and to discriminatemore effectively between stent designs.

2011 - Numerical simulation of forced convection over a periodic series of rectangular cavities at low Prandtl number [Articolo su rivista]
Stalio, Enrico; Angeli, Diego; Barozzi, Giovanni Sebastiano
abstract

Convective heat transfer in laminar conditions is studied numerically for a Prandtl number Pr = 0.025,representative of liquid lead–bismuth eutectic (LBE). The geometry investigated is a channel with a periodicseries of shallow cavities. Finite-volume simulations are carried out on structured orthogonal curvilineargrids, for ten values of the Reynolds number based on the hydraulic diameter between Rem = 24.9and Rem = 2260. Flow separation and reattachment are observed also at very low Reynolds numbers andwall friction is found to be remarkably unequal at the two walls. In almost all cases investigated, heattransfer rates are smaller than the corresponding flat channel values. Low-Prandtl number heat transferrates, investigated by comparison with Pr = 0.71 results, are large only for uniform wall temperature andvery low Re. Influence of flow separation on local heat transfer rates is discussed, together with the effectof different thermal boundary conditions. Dependency of heat transfer performance on the cavity geometryis also considered.

2011 - Numerical simulation of weakly turbulent heat transfer over cavities at low Prandtl numbers [Relazione in Atti di Convegno]
Errico, Orsola; Stalio, Enrico; Barozzi, Giovanni Sebastiano
abstract

Heat transfer investigations at low Prandtl number values are of interest for different applications, but reliable physicalmodels for turbulent convection in these fluids are still missing. In the present study forced convective heat transfer isinvestigated numerically for weakly turbulent flow in a streamwise periodic channel with cavities. Simulations are performedfor different values of the Prandtl number, with the focus on the case with Prandtl number equal to 0:025, which representsliquid lead-bismuth eutectic (LBE). In the paper the main features of the mean and instantaneous flow field are presentedtogether with first order statistics. The influence of flow separation mechanisms and turbulent mixing on local and globalheat transfer rates are discussed, for both isoflux and isothermal boundary conditions (BCs hereafter). The numericalcode used for the simulations is based on a second order, finite volume algorithm, implemented over structured, curvilinearmesh. This work aims to contribute to the development of physical model of turbulent convection for low Prandtl numberfluid flows, by providing information for both velocity and temperature fields.

2011 - Routes to chaos in confined thermal convectionarising from a cylindrical heat source [Relazione in Atti di Convegno]
Angeli, Diego; A., Pagano; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

Natural convection ows arising from a horizontal cylinder centred ina square-sectioned enclosure are studied numerically. The sequence of bifurcations marking the transition of base fixed-point solutions to unsteady, chaotic ows is followed for increasing values of the Rayleigh number, and for two values of the enclosure aspect ratio, A. It is observed that, for the lower A-value, the route to chaosis triggered by a supercritical Hopf bifurcation, followed by a sequence of period- doublings, while, for the higher A-value, the symmetry of the system is broken by a pitchfork bifurcation, with periodic orbits originating from both branches, and eventually approaching chaos, exhibiting features typical of blue-sky catastrophes.

2010 - A Comprehensive Review of Natural Convection in Triangular Enclosures [Articolo su rivista]
O. M., Kamiyo; Angeli, Diego; M. W., Collins; Barozzi, Giovanni Sebastiano; V. O. S., Olunloyo; S. O., Talabi
abstract

Natural convection in triangular enclosures is an important problem. It displays well the generic attributes of this class of convection, with its dependence on enclosure geometry, orientation and thermal boundary conditions. It is particularly rich in its variety of flow regimes and thermal fields as well as having significant practical application. In this paper, a comprehensive view of the research area is sought by critically examining the experimental and numerical approaches adopted in studies of this problem in the literature. Different thermal boundary conditions for the evolution of the flow regimes and thermal fields are considered. Effects of changes in pitch angle and the Rayleigh number on the flow and thermal fields are examined in detail. Although most of the past studies are in the laminar regime, the review extends up to the recent studies of the low turbulent regime. Finally, areas of further research are highlighted.

2010 - A Critical Review of Buoyancy-induced Flow Transitions in Horizontal Annuli [Articolo su rivista]
Angeli, Diego; Barozzi, Giovanni Sebastiano; M. W., Collins; O. M., Kamiyo
abstract

The main mechanisms of transition of buoyancy-induced flows in the horizontal annulus betweencircular cylinders are reviewed, based on the available literature. Both experimental and theoreticalstudies are considered. The different scenarios for the evolution of the flow regimes and temperaturepatterns are tracked, for increasing values of the Rayleigh number, Ra. The occurrence of variousinstability and bifurcative phenomena is pointed out, and linked to other relevant parameters, such asthe radius ratio R and the Prandtl number, Pr. Although most of the relevant literature is on 2D cases, theeffect of the third dimension is considered as far as possible. Studies on the influence of the eccentricityof the inner cylinder on the laminar flow and the thermal asset are also reviewed. Finally, open questionsand topics for future research are hinted at.

2010 - Beyond the Virtual Intracranial Stenting Challenge 2007: non-Newtonian and flow pulsatility effects [Articolo su rivista]
Cavazzuti, Marco; M. A., Atherton; M. W., Collins; Barozzi, Giovanni Sebastiano
abstract

Three models of stented cerebral aneurysms, originating from the VirtualIntracranial Stenting Challenge 2007 (visc'07), are meshed and the owcharacteristics simulated using commercial Computational Fluid Dynamics(cfd) software. Following views expressed in the literature and consistentwith the recommendations of a report, the eects of non-Newtonian viscos-ity and pulsatile ow are implemented. Conventional graphical Wall ShearStress (wss) output and basic summary measures of wss are normally usedas a qualitative means of comparing the cfd simulations. Herein a quan-titative measure of stent performance using wss distribution is presented,which clearly discriminates in favour of the stent design identied by theother groups in the report and provides a more informative comparison. Weconclude that non-Newtonian and pulsatile eects are important to includein order to avoid underestimating wss and to discriminate more eectivelybetween stent designs.

2010 - Direct Numerical Simulation of Forced Convection over Steps at Low Prandtl Number [Relazione in Atti di Convegno]
Angeli, Diego; Barozzi, Giovanni Sebastiano; Errico, Orsola; Stalio, Enrico; Tartarini, Paolo
abstract

Convective heat transfer in transitional and weakly turbulent conditions is investigated numerically for a Prandtl number Pr =0.025, representative of liquid lead-bismuth eutectic (LBE). The geometry selected is a periodic channel with cavities. Finitevolumesimulations are carried out on structured orthogonal curvilinear grids, for two different values of the Reynolds numberin the weakly turbulent range. The main features of the mean and instantaneous flow fields are described. The influence of flowseparation mechanisms and turbulent mixing on local and global heat transfer rates is also discussed, considering the effect ofdifferent thermal boundary conditions imposed at the channel walls.

2010 - Flow Transitions and Bifurcations of Buoyancy-induced Flows from an Eclosed Cylindrical Heat Source [Relazione in Atti di Convegno]
Angeli, Diego; A., Pagano; Corticelli, Mauro Alessandro; A., Fichera; Barozzi, Giovanni Sebastiano
abstract

The study presents a numerical analysis of the dynamics of transitional natural convection flow regimes, generated by a confined thermal source. The system considered is a 2D enclosure of square cross-section, containing a horizontal cylindrical source,placed in central position. The heat carrier fluid is air with Prandtl number Pr = 0:7. The resulting flow is investigated withrespect to the variation of the Rayleigh number, based on the minimum gap width H between the cylinder and the enclosurewalls. Three values of the aspect ratio A are considered (A = 2:5; 3:¯3; 5;). The numerical scheme is based on a second orderfinite-volume discretization of the Navier-Stokes equations, solved on orthogonal Cartesian grids. Internal boundaries nonalignedwith the grid are subjected to special treatment. The first bifurcation of the low-Ra fixed-point solution is tracked foreach A-value. The transition to unsteady, chaotic flow is detailed for A = 2:5. The supercritical behaviour of the system isinvestigated using nonlinear analysis tools and phase space representations of the computed time series, and the effect of the flow features on heat transfer is discussed.

2010 - Flow Transitions and Bifurcations of Buoyancy-induced Flows from an Enclosed Cyindrical Heat Source [Relazione in Atti di Convegno]
Angeli, Diego; A., Pagano; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

This study presents a numerical analysis of the dynamics of transitional natural convection flow regimes, generated by a confined thermal source. The system considered is a 2D enclosure of square cross-section, containing a horizontal cylindrical source, placed in a central position. The heat carrier fluid is air with Prandtl number Pr = 0.7. The resulting flow is investigated with respect to the variation of the Rayleigh number, based on the minimum gap width H between the cylinder and the enclosure walls. Three values of the aspect ratio A are considered (A = 2.5; 3.3; 5). The first bifurcation of the low-Ra fixed-point solution is tracked for each A-value. The transition to unsteady, chaotic flow is detailed for A = 2.5. The supercritical behaviour of the system is investigated using nonlinear analysis tools and phase space representations of the computed time series.

2009 - A comprehensive review on buoyancy-induced flow transitions in horizontal annuli [Relazione in Atti di Convegno]
Angeli, Diego; Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro
abstract

The main mechanisms of transition of buoyancy-inducedflows in horizontal annuli are reviewed, based on the availableliterature. Both experimental and theoretical studies areconsidered. The different scenarios for the evolution of theflow regimes and temperature patterns are tracked, for increasingvalues of the Rayleigh number, Ra. The occurrenceof various instability and bifurcative phenomena is pointedout, and linked to other relevant parameters, such as the radiusratio, R and the Prandtl number, Pr. The effect of theaxial dimension is also considered. Finally, possible futureresearch issues on the subject are briefly hinted at.

2009 - Building structures with high thermal inertia based on phase change materials [Articolo su rivista]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; Libbra, Antonio; Muscio, Alberto; Tartarini, Paolo
abstract

In order to ensure the comfort of people who inhabit a building, the building envelope must have thermal inertia great enough to dampen its temperature fluctuations, in particular those due to the solar cycle. The use of materials that can accumulate large amounts of heat in the form of phase change latent heat, the so-called PCM, represents a very interesting approach to make buildings reactive to cyclical thermal loads and achieve better thermal performance with the same wall thickness, or the same thermal performance with reduced wall thickness.The present work is focused onto the development of roofs with small surface mass and high thermal inertia thanks to the integration of PCM. In particular, the relationship between properties of the PCM and thermal behaviour of the roof structure is investigated by numerical simulation. Moreover, the more convenient position of the PCM layer with respect to the thermal insulation layer is investigated for some typical structures to be protected against summer overheating.

2009 - Optimization of heat exchanger enhanced surfaces under turbulent conditions [Relazione in Atti di Convegno]
Cavazzuti, Marco; Angeli, Diego; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

The optimization of heat transfer enhancing surfaces for compact heat exchangers is discussed.The heat transfer passages are parameterized through Bézier curves, and the optimum choice of the parameters is sought using both multi-objective and single objective optimization techniques. The objectives of the optimization are the maximization of the heat transfer rate and the minimization of the pressure drop encountered by the fluid crossing the passage. The objectives are evaluated in nondimensional form in terms of the Nusselt number and the friction factor. The investigation is carried out by means of CFD analyses, the fluid flowing in the passages is air, and turbulent flow is assumed. Two different turbulence models (namely, k- and k-!) are adopted in the optimization processes and the effect of the choice of the turbulence model on the optimization outcome is discussed.

2008 - I codici commerciali per la Termofluidodinamica Computazionale [Capitolo/Saggio]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; Levoni, Paolo
abstract

Si affrontano alcune problematiche relative all'utilizzo dei codici commerciali per la CFD

2008 - Influence of the Prandtl Number on Buoyancy-Induced Flow and Heat Transfer from an Enclosed Cylindrical Heat Source [Relazione in Atti di Convegno]
Angeli, Diego; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

A numerical study of the natural convection flow arising from a confined thermal source is presented. The physical systemconsidered is a 2D enclosure of square cross-section, containing an isothermal horizontal cylindrical source. The heating body iscentred in the enclosure, and the resulting flow is investigated with respect to the effect of the Prandtl number, for different valuesof the Rayleigh number and of the aspect ratio. The numerical scheme is based on a second order finite-volume discretization ofthe Navier-Stokes equations, solved on orthogonal Cartesian grids. Internal boundaries non-aligned with the grid are subjectedto special treatment. The work focuses on the onset of steady and transitional flows. The asymptotic flow and thermal patternsare investigated, as well as the heat transfer performance of the system

2008 - Numerical Predictions for Stable Buoyant Regimes within a Square Cavity Containing a Heated Horizontal Cylinder [Articolo su rivista]
Angeli, Diego; P., Levoni; Barozzi, Giovanni Sebastiano
abstract

Buoyancy-induced flow regimes are investigated numerically for the basic case of a horizontal cylinder centred into a long co-axial square-sectioned cavity. In the frame of the 2D assumption, the treshold for the occurrence of time-dependent behaviour is explored. Stable symmetric and non-symmetric steady-state solutions, as well as unsteady regimes are observed, depending on the Rayleigh number, Ra, and the aspect ratio of the cavity, d. Four d-values are considered (d = .2, .4, .6, and .8). Heat transfer results are correlated by a single equation covering the full subcritical region.

2008 - Turbulence Models comparison in heat exchanger enhanced surfaces optimization [Relazione in Atti di Convegno]
Cavazzuti, Marco; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

In this paper the problem of the optimization of heat transfer enhancing surfaces is faced. The surfaces are parameterized usingBezier curves and solved with a finite volumes CFD code. The optimization is based on three different algorithms used in cascade:MOGT, MOGA-II and simplex for non-linear optimization. The Reynolds number is based on the average velocity and hydraulicdiameter of the channels and is set to 1000, the Prandtl number is 0:744. The same optimization process is carried out twice usingtwo different turbulence models: k-e RNG with enhanced wall treatment and k-w SST with low Reynolds number correction to theturbulent viscosity. It is found that the differences in the optimum channel shapes are significant and even that the same channelcan give quite different results being solved with a turbulence model or another. Though, from the results of the two optimizationprocesses, the rules of thumb we can infer on which elements a channel needs in order to have a certain performance, are almostthe same.

2008 - Vascular device interaction with the endothelium [Abstract in Atti di Convegno]
M. A., Atherton; A. W., Khir; Cavazzuti, Marco; Barozzi, Giovanni Sebastiano; M. W., Collins
abstract

The interaction between cerebral stents and endothelium, as well as the interaction between intra aortic balloon pumps, temporary cardiac assist devices, with aortic tissues are described in view of the numerical modelling of the above vascular devices.

2007 - Appendice di Deriva I.A.C.C.: Soluzione Numerica Turbolenta [Relazione in Atti di Convegno]
Levoni, Paolo; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

Il presente lavoro si propone di testare le potenzialità di un codice CFD Navier-Stokes ai volumi finiti nella soluzione delcampo idrodinamico relativo ad un’appendice di deriva per imbarcazioni a vela da competizione. In particolare, è stata studiata una configurazione deriva-bulbo I.A.C.C. (International America’s Cup Class), avvalendosi del codice industriale Fluent 6.2 (©ANSYS Inc.). Il complesso comportamento operativo di un sistema di tale tipologia presenta diversi fenomeni idrodinamici di difficile previsione numerica; pertanto il sistema descritto è stato ritenuto un significativo test case per la valutazione delle diverse tecniche di simulazione. I risultati ottenuti sono stati confrontati con dati sperimentali reperiti in letteratura.Sono state esaminate le prestazioni di diversi modelli di turbolenza R.A.N.S. (Reynolds Averaged Navier Stokes), sia di tipo eddy viscosity che Reynolds stress, e del più complesso modello DES (Detached Eddy Simulation). Le simulazioni sono state effettuate avvalendosi di griglie di calcolo di diversa risoluzione, al fine di poter utilizzare in maniera ottimale sia formulazioni low-Reynolds che high-Reynolds. Le comparazioni numerico-sperimentali hanno evidenziato l’idoneità di ciascuno schema alla soluzione del sistema fluidodinamico in oggetto, l’accuratezza ed il relativo onere computazionale.

2007 - Preliminary Analysis of the Dynamics of Buoyancy-driven Flows from an Enclosed Cylindrical Heat Source [Relazione in Atti di Convegno]
Angeli, Diego; Barozzi, Giovanni Sebastiano; A., Fichera; A., Pagano
abstract

The study presents a numerical analysis of the dynamics of time-dependent natural convection flow regimes, generated by a con- fined thermal source. The physical system considered is a 2D cavity of square cross-section, containing a horizontal cylindrical source, placed in central position. The heat carrier fluid is air at Prandtl number Pr = .7. The resulting flow is investigated with respect to the variation of the Grashof number, based on the gap between the upper cavity wall and the cylinder top. The relative dimensions of both cavity and source are fixed. The numerical scheme is based on a second order finite-volume discretization of the Navier-Stokes equations, solved on orthogonal Cartesian grids. Internal boundaries non-aligned with the grid are subjected to special treatment. Computations are carried out for four supercritical values of the Grashof number. Some preliminary con- siderations are drawn on the dynamical behaviour of the system, while representing the attractors of the computed time series in phase space, and observing their morphological structure.

2007 - Ricerca di mine mediante termografia infrarossa: analisi dell’influenza dell’umidità superficiale [Relazione in Atti di Convegno]
L., Tarozzi; Muscio, Alberto; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

Il problema dell’individuazione di una mina antiuomo sotterrata è estremamente complesso e di difficile soluzione. Attualmente, la ricerca manuale mediante sondino ad asta costituisce l’approccio più efficace per le attività di bonifica di un’area minata, ma comporta tempi estenuanti e pericoli notevoli per il personale addetto. È quindi evidente la necessità di sviluppare tecniche alternative. Fra queste, si presenta molto interessante la ricerca mediante termografia infrarossa.Questo studio si inserisce in un filone di ricerca da tempo avviato presso il Dipartimento di Ingegneria Meccanica e Civile di Modena, vertente sullo sviluppo di metodologie di indagine che consentano di prevedere ed incrementare l’affidabilità della ricerca di mine antiuomo tramite termografia all’infrarosso. In questa sede, l’analisi ha riguardato l’effetto dell’umidità superficiale del suolo sulla segnatura termica della mina, cioè sul contrasto tra temperatura superficiale del terreno sopra la mina e temperatura superficiale del terreno circostante. Si è a tal scopo impiegato un apparato sperimentale sviluppato nel corso di precedenti attività di ricerca, che consente di riprodurre con scala spaziale e temporale ridotta il comportamento termico un campo minato e le condizioni ambientali che lo caratterizzano. Gli esperimenti svolti hanno mostrato che l’umidificazione del terreno può incrementare notevolmente la segnatura termica della mina e può essere quindi sfruttata per aumentare le probabilità di individuazione.

2007 - Thermographic analysis of flow distribution in compact heat exchangers for a Formula 1 car [Articolo su rivista]
E., Caffagni; Levoni, Paolo; M., Piraccini; Muscio, Alberto; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

A non-intrusive approach is investigated to calculate the internal flow distribution in heat exchangers. In particular, the liquid flow rate can be determined in each tube of an air-liquid finned-tube heat exchanger. A purposely designed test bench impresses a sudden change of temperature of the liquid flowing through the heat exchanger. The thermal transient that follows is monitored by a thermographic camera. This measures the rise of surface temperature along each tube. The temperature evolution pattern is then correlated to the flow rate in the tube by simple mathematical processing. The heat exchanger is tested in still air. Modification is not required. The approach is tested on heat exchangers for a F1 race car, with encouraging results. (c) 2006 Elsevier B.V. All rights reserved.

2006 - Confronto fra tecniche PIV e UPDV per misure di velocità in convenzione naturale in una cavità chiusa contenente una sorgente termica [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Levoni, Paolo; Stalio, Enrico; Tarozzi, Luca
abstract

tecniche PIV e UPDV, per la determinazione dei campi di velocità nei fluidi in moto, vengono per la prima volta comparate nell’ambito di uno stesso esperimento relativo ai moti di convezione naturale indotti da una sorgente termica all’interno di una cavità chiusa. L’esperimento viene condotto utilizzando una resistenza termica cilindrica orizzontale in una cavità allungata a sezione quadrata, contenente acqua. Il caso analizzato è caratterizzato da numeri di Rayleigh modificato e Prandtl rispettivamente pari a Ra=17400 e Pr=8.03. Il confronto tra tecniche PIV e UPDV è svolto sia in termini quantitativi, determinando l’accuratezza e la precisione di misura, che evidenziando parametri qualitativi, quali la complessità d’uso della strumentazione nel particolare caso di studio. L’accuratezza delle tecniche di misura è anche stimata in riferimento alla risoluzione numerica del problema ottenuta mediante tecnica di simulazione numerica (DNS). Si descrivono l’apparato sperimentale, le procedure di rilevazione della velocità e gli esiti sulla comparazione tra le due tecniche di misura. L’indagine mostra che, nell’ambito dell’esperimento svolto, la tecnica PIV dimostra maggiore precisione, mentre la stima dell’accuratezza porta a risultati analoghi per le due tecniche; entrambe denunciano limiti in prossimità delle pareti solide.

2006 - Numerical Analysis of Natural Convection Flow and Heat Transfer from an Enclosed Cylindrical Heat Source [Relazione in Atti di Convegno]
Angeli, Diego; P., Levoni; E., Caffagni; Barozzi, Giovanni Sebastiano
abstract

A numerical study of the natural convection flow arising from a confined thermal source is presented. The physical system considered is a 2D cavity of square cross-section, containing a horizontal cylindrical source, the heat carrier fluid being air at Prandtl number Pr = .7. The heating body is placed in central position; the resulting flow is investigated with respect to the variation of the Rayleigh number and the ratio between the source diameter and the cavity side length. Either Dirichlet and Neumann thermal boundary conditions are imposed on the cylinder surface. The analyses make use of two Navier-Stokes, finite- volume codes: a general-purpose CFD package, and a Direct Numerical Simulation software. Main issues of the work are the rise of steady and transitional flows and the heat transfer performance of the system, as influenced by the different boundary conditions at the heat source wall. A correlating equation for the average Nusselt number on the cylinder, previously obtained for the isothermal case, is validated for the uniform heat flux condition.

2005 - I cool roofs, una soluzione innovativa per il risparmio energetico in edilizia [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; Muscio, Alberto; Tartarini, Paolo
abstract

I cool roofs sono tetti contraddistinti da elevata capacità di riflettere l’irradiazione solare incidente e, al contempo, di emettere energia termica nell’infrarosso. Essi possono fornire un’efficace soluzione al problema del surriscaldamento estivo dei singoli edifici e delle grandi aree urbane.In California e in altri Stati degli U.S.A. i cool roofs sono da molti anni oggetto di analisi tecnico-economiche estensive e, più recentemente, di attività di certificazione e regolamentazione. In Italia, invece, sebbene le condizioni climatiche di buona parte della penisola siano tali da rendere conveniente l’installazione di cool roofs, questi sembrano sconosciuti ai più. Studi in materia sono stati perciò avviati dal Dipartimento di Ingegneria Meccanica e Civile di Modena.In questa relazione si illustra il funzionamento dei cool roofs dal punto di vista fisico. In particolare, si analizzano gli effetti che le diverse proprietà emissive hanno sulle temperature raggiunte dal tetto e sul calore che lo attraversa. Si delineano inoltre i principali programmi di attestazione delle proprietà e di incentivazione avviati degli U.S.A. e la situazione di mercato.

2005 - Radiative properties of Surfaces and energy saving in buildings: the cool roofs [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; Muscio, Alberto; L., Tarozzi; Tartarini, Paolo
abstract

Cool roofs are building coverings having high reflectance to solar radiation and high emittance in the infrared range. They can provide an effective solution to building overheating during hot seasons.In the U.S.A. the cool roofs have been investigated extensively. Certification procedures have also been developed by independent bodies, and certified roof products are commercially available.In the aim of verifying the potential of cool roof technologies for the Italian climate, an investigation was started at the Dept. of Mechanical and Civil Engineering at Modena.Early results are presented for an experimental cool roof. The work is completed with an analysis of the thermal behavior of a typical low-slope roof and a brief review of existing certification programs and commercially available products.

2005 - Rilievi di velocità in regime di convezione naturale mediante tecnica "pulsed doppler ultrasound" in un cavità contenente una sorgente termica [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Muscio, Alberto; L., Tarozzi
abstract

Oggetto del presente studio è l’analisi sperimentale del campo di moto in regime di convezione naturale all’interno di una cavità parallelepipeda contenente un fluido, in cui è immersa una sorgente termica orizzontale di forma cilindrica. Per la misura della velocità del fluido si utilizza la tecnica “Ultrasound Pulsed Doppler Velocimetry” (UPDV), che permette di effettuare misure non intrusive e, in linea di principio, di ricostruire l’intero campo di moto. L’applicabilità della tecnica non è ancora stata verificata a fondo in regimi di convenzione naturale.Si descrivono in questo lavoro l’apparato sperimentale che è stato realizzato, la procedura di rilevazione della velocità e quella di ricostruzione del campo di moto su una sezione verticale mediana della cavità parallelepipeda. Le principali criticità poste dalla tecnica di misura e dal particolare ambito di applicazione vengono evidenziate attraverso la presentazione dei risultati sperimentali ottenuti. Infine, si confrontano i risultati sperimentali con quelli forniti da simulazioni numeriche CFD.

2005 - Thermographic analysis of flow distribution in compact heat exchangers for a Formula 1 car [Abstract in Atti di Convegno]
E., Caffagni; Levoni, Paolo; Muscio, Alberto; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano; M., Piraccini
abstract

THERMOGRAPHIC ANALYSIS OF FLOW DISTRIBUTIONIN COMPACT HEAT EXCHANGERS FOR A FORMULA 1 CAR

2004 - A Numerical Investigation on Convective Accelerometer [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; C., Bussi; Corticelli, Mauro Alessandro
abstract

Aim of this paper is to investigate an innovative, low – cost, non-intrusive technique for measuringan arbitrary acceleration vector, belonging to a reference plane. The technique is based on freeconvection and allows computing the acceleration magnitude as a function of the temperatureimbalance across four sensors, located within a cavity. The dual-axis convective accelerometermakes use of the relationship existing between the Grashof number and the acceleration vector. Thetechnique shows good linearity, sensitivity and frequency response. The use of a four-sensor clusterallows obtaining the acceleration direction. The shape and the size of the enclosure, as well as thelocation and the number of sensors considerably affect the response of the system. Therefore, aparametric analysis is carried out by numerical simulation. Finally, some hints are provided for thedesign and the tuning of the measuring device. The numerical simulation is carried out using afinite-volume-based ‘projection method’, accurate to the 2nd order in both space and time.Some hints for the designer are finally given based on the dimensional analysis of the device.

2004 - A fast Cartesian scheme for unsteady heat diffusion on irregular domains [Articolo su rivista]
Barozzi, Giovanni Sebastiano; C., Bussi; Corticelli, Mauro Alessandro
abstract

A numerical integration method is presented for the treatment of transient heat conduction problems. A Cartesian formulation is developed that is suitable for the treatment of irregular domains under general boundary conditions. The qualities of the scheme are demonstrated, in terms of both accuracy and computational efficiency, by comparison with analytical and numerical solutions. Results for the basic two-dimensional annular geometry show that the method has nearly second-order accuracy in space and time, at least in simple cases. Finally, a complex multiconnected domain is considered, to test the method performance under more severe conditions, including the presence of multiple length scales. The numerical experiment demonstrates that the numerical scheme is efficient, stable, and convergent.

2004 - CFD ananlysys onf the impact of convection in a new modeification of the Ångstroem’s method [Relazione in Atti di Convegno]
Levoni, Paolo; Muscio, Alberto; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

measurement was developed. Its novelty is that harmonic thermal waves with mean value equal to the ambient temperature are induced in the specimen by a purposely developed source. This allows estimating the diffusivity by relatively simple processing of surface-temperature data.The estimate is based on a mathematical model, in which the unknown coefficient of surface heat transfer is assumed to be uniform and constant. The coefficient can thus be eliminated by combining information from amplitude decay and phase velocity of the thermal waves.This work is aimed at verifying the assumption of uniform and constant heat transfer coefficient. A parametric analysis is performed by CFD simulation of the test system.

2004 - I Codici Commerciali [Capitolo/Saggio]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; F., Inzoli
abstract

Il capitolo analizza le problematiche collegate all'utilizzo de codici commerciali o industriali in termofluidodinamica

2004 - Influenza della convezione e dell'irraggiamento nella misura della diffusività termica mediante una nuova variante del metodo di Angstroem [Relazione in Atti di Convegno]
C., Bussi; Muscio, Alberto; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

Una nuova variante del metodo di Angstroem consente di stimare, attraverso un’analisi relativamente semplice di misure termografiche nell’infrarosso, la diffusività termica di un materiale solido. La diffusività è correlata alle modalità con cui un’oscillazione termica si propaga in un campione del materiale in esame. La semplicità dell’analisi è conseguenza del fatto che l’oscillazione termica applicata al campione, prodotta tramite un dispositivo appositamente sviluppato, è perfettamente armonica e con valore medio pari alla temperatura ambiente.La procedura di stima della diffusività è basata su una formulazione matematica, in cui si assume costante ed uniforme il coefficiente di scambio termico sulle superfici del campione esposte all’aria. Sotto tale ipotesi, la determinazione del coefficiente di scambio termico, che è in generale incognito, è superflua ai fini della determinazione della diffusività.In questo lavoro si riportano i risultati di un’analisi parametrica dei fenomeni di scambio termico superficiale, effettuata tramite metodi numerici e volta, da una parte, a verificare l’ipotesi di uniformità del coefficiente di scambio termico, dall’altra, ad investigare approcci atti a minimizzare l’impatto dei fenomeni convettivi sull’accuratezza della stima della diffusività.

2004 - LA CHIESA DI SANTA MARIA DELLA PIETA' IN BOLOGNA :UNA CONOSCENZA APPROFONDITA PER UNA CORRETTA PROGETTAZIONE [Articolo su rivista]
Barozzi, Giovanni Sebastiano; Dumas, Antonio; V., Lucchese; P., Todesco
abstract

Un excursus storico architettonico sulle chiese gesuitiche del Seicento ha messo im risalto gli elemnti strutturali che hanno contribuito a realizzare lecondizioni di instabilità dinamica e di turbolenza dell'aria pur in presenza d una bassa disuniformità termica dell'aria (meno di mezzo grado centigrado), localizzata solo in alcune situazioni sulle pareti esul soffitto. Ciò consente di prevedere per quel tipo di chiese una condizione analoga, anche se le msure mettono in evidenza la possibilità di un innesco di turbolenza anche solo per ambienti di grandi dimensioni.

2004 - Modellazione di transizione dello strato limite con modelli di turbolenza R.A.N.S. [Relazione in Atti di Convegno]
Levoni, Paolo; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

le tecniche numeriche di simulazione termofluidodinamica CFD godono di una notevole diffusione, ma l’onere computazionale che la soluzione diretta dell’equazione di Navier-Stokes comporta (Direct Numeric Simulation), ha determinato un significativo incremento di popolarità dell’approccio R.A.N.S., specialmente in ambiente industriale.Tuttavia nei codici Navier-Stokes industriali non sono stati ancora implementati i modelli tridimensionali di transizione attualmente disponibili, in quanto essi non risultano ancora sufficientemente accurati ed affidabili; pertanto risulta indispensabile, nell’ambito della progettazione navale di barche a vela, la definizione di una tecnica semi-empirica per la riproduzione del fenomeno, finalizzata ad una più realistica valutazione dell’azione tangenziale.A tale scopo è stato analizzato il sistema elementare rappresentato da una lastra piana in assenza di gradiente di pressione nella direzione del flusso, in relazione ad una serie di test sperimentali reperiti in letteratura, effettuati con differenti valori dell’intensità di turbolenza asintotica, quindi con diverse posizioni della zona di transizione

2004 - Ventilazione naturale turbolenta nei grandi ambienti dotati di impianti di riscaldamento a pavimento: analisi e soluzioni nella Chiesa di S. Maria della Pietà in Bologna [Relazione in Atti di Convegno]
S., Anzillotti; Barozzi, Giovanni Sebastiano; Dumas, Antonio; P., Proli
abstract

Si decrivono i risultati sperimentali e numerici relativi al caso di riscldamento a pavimento di un luogo di culto di grandi dimensioni.Si presentano le soluzioni tecniche adottate per ridurre gli inconvenienti derivanti dall'intensità delle circolazioni di convezione naturale che la tipologia di impianto adottata provoca nei grandi mabienti.

2003 - Osservazioni critiche sull'utilizzo di modelli di turbolenza R.A.N.S. e relative condizioni al contorno in applicazioni di idrodinamica esterna [Relazione in Atti di Convegno]
Levoni, Paolo; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

Il presente lavoro si propone di testare le potenzialità di modelli di turbolenza di tipo RANS, nell’ambitodell’analisi idrodinamica bidimensionale di un profilo laminare, immerso in un flusso stazionario a bassa intensità diturbolenza; tale sezione, di caratteristiche e prestazioni note, è rappresentativa delle tipologie di geometrie utilizzatenel design delle appendici di imbarcazioni a vela da competizione.Scopo della ricerca è definire i limiti di applicabilità e l’accuratezza predittiva delle tecniche di discretizzazione aivolumi di controllo e dei modelli di turbolenza kε-RNG, kω-SST e Spalart-Allmaras, implementati nel codiceindustriale FLUENT, versione 6.0; si intende inoltre evidenziare l’importanza che in questa tipologia di sistemiriveste una oculata scelta delle condizioni al contorno, e come queste influenzino il campo di turbolenza.Il confronto tra risultati numerici e dati sperimentali evidenzia il buon livello di accuratezza che questemetodologie permettono di raggiungere con un costo computazionale ragionevole, sia in termini di potenza che ditempi di calcolo

2003 - Simulazione di moti di convezione naturale all'interno di una cavità confinata contenente una sorgente termica [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; C., Bussi; Corticelli, Mauro Alessandro
abstract

In questo lavoro viene presentato un modello di calcolo per lo studio dei moti di convezione naturale presenti all’interno di cavità chiuse di forma arbitraria, riscaldate da sorgenti interne sempre di forma arbitraria. Lo scopo è quello di fornire uno strumento per l’integrazione diretta delle equazioni del moto,nella loro forma instazionaria adimensionale. Tale strumento è, in ultima analisi, finalizzato allo studio delle modalità di scambio termico diffusivo – convettivo all’interno di cavità chiuse.In questo articolo è presentata una soluzione originale, finalizzata all’integrazione numerica del campo di moto, attraverso una discretizzazione ai volumi finiti su griglia cartesiana, all’interno di geometrie complesse. Lo schema di calcolo proposto è quindi applicato allo studio di due problemi di scambio termico convettivo, per i quali sono dati sperimentali e risultati numerici ottenuti attraverso codici di calcolo tradizionali. L’analisi dei risultati locali e dei coefficienti globali di scambio termico conferma l’accuratezza del metodo di calcolo.

2003 - Un modello numerico per l’analisi termodinamica di motori Stirling–Beale [Relazione in Atti di Convegno]
Borghi, Massimo; M., Bonnici; Cavazzuti, Marco; Barozzi, Giovanni Sebastiano
abstract

Si presenta un modello simulativo applicabile ai motori lineari a pistoni liberi a ciclo Stirling, secondo lo schema proposto da Beale. Il modello si basa sulla discretizzazione temporale delle equazioni del moto dei pistoni e delle equazioni di bilancio di massa e di energia per il volume di lavoro della macchina. Il modello è destinato all’esecuzione di analisi di stabilità e di efficienza di soluzioni progettuali alternative, in sede di dimensionamento dei dispositivi

2002 - Comparazione tra Modelli di Turbolenza nello Studio Numerico della Perdita di Carico dovuta ad un Restringimento in un Condotto [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; D., Manicardi
abstract

Vengono studiate per via numerica cinque differenti configurazioni geometriche per un sistema composto da un condotto a sezione quadrata che presenta un restringimento a sezione circolare. Lo studio viene svolto utilizzando il software FLUENT, facendo uso, per ciascuna configurazione, dei modelli di turbolenza k- standard, k- RNG e RSM, al fine di valutarne comparativamente le potenzialità ed i limiti, nel contesto della previsione delle perdite di carico concentrate in condotti.L’indagine si riferisce a condizioni di regime stazionario, per un valore del numero di Reynolds pari a 1x105, considerando acqua quale fluido operatore.L’indagine evidenzia una spiccata sensibilità delle soluzioni sia alla conformazione della griglia di calcolo che alla scelta del modello di turbolenza adottato.

2001 - Comparazione tra Modelli di Turbolenza nello Studio Numerico dell’Interazione di Getti Liberi [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; Manicardi, D.
abstract

La presente ricerca è principalmente diretta a verificare le potenzialità di pratico impiego dei tradizionali modelli di turbolenza nell’ambito della modellizzazione termofluidodinamica di dispositivi industriali. Vengono qui studiate per via numerica due configurazioni di getti liberi interagenti con valori del numero di Reynolds dell’ordine di 105; entrambe le configurazioni sono costituite da getti in parete sottile emergenti in un ambiente in quiete da un sistema di quattro fori; nel primo caso a sezione circolare e nel secondo a sezione quadrata. Lo studio è stato compiuto con lo scopo di definire i limiti di applicabilità e l’accuratezza predittiva delle tecniche di discretizzazione ai volumi di controllo e dei correnti modelli di turbolenza k-ε standard, k-ε RNG e RSM ed utilizzando il software FLUENT versione 5.0 della Fluent Inc., Lebanon N.H. USA. Si presentano gli esiti delle simulazioni, individuando le zone tipiche dei getti liberi interagenti e altri parametri di interesse industriale.

2001 - Simulazione numerica della convezione naturale in cavità contenenti cilindri riscaldanti in quiete o in rotazione [Relazione in Atti di Convegno]
Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano; Cremaschi, L.
abstract

Lo studio si propone la previsione numerica dei campi termici e dinamici di convezione naturale, prodotti da un cilindro orizzontale a temperatura costante, posto in quiete o in rotazione, immerso in aria, all’interno di una cavità a sezione rettangolare. Le simulazione numeriche sono state condotte utilizzando un codice di calcolo sviluppato per lo studio della convezione naturale in cavità e condotti a sezione rettangolare su griglia cartesiana non uniforme, in cui è stata implementata una procedura che permette di considerare la presenza di oggetti immersi anche a geometria non cartesiana, con una maggiore flessibilità rispetto ai possibili casi analizzabili, mantenendo il tempo di calcolo entro limiti più che accettabili.Il modello è in grado di rappresentare adeguatamente i fenomeni di scambio termico all’interno dei cavità chiuse, sia per regimi stazionari che dipendenti dal tempo.Dove possibile, i risultati sono stati confrontati con quelli ottenuti da prove sperimentali disponibili in letteratura, potendo così convalidare il corretto funzionamento di questo nuovo strumento di analisi.

2000 - Combined Free and Forced Convection in Horizontal Flows: a Review [Capitolo/Saggio]
S., Piva; Barozzi, Giovanni Sebastiano; M. W., Collins
abstract

Numerical methods used to trat combined convection within horizontal and inclined tubes are reviewed, and perspectives for future developments are outlined.

2000 - Comparazione fra modelli di tubolenza nello studio numerico di getti sommersi [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; S., Fantoni
abstract

Si considerano per via numerica due configurazioni di sistemi a getto, l’una relativa all’immissione di aria in ambiente libero, l’altra relativa all’efflusso in ambiente semiconfinato di liquido refrigerante FC77. L’indagine propone il confronto tra i tre modelli di turbolenza k-epsilon standard, k-epsilon RNG e RSM

2000 - Effect of Thermal Boundary Conditions in the Numerical Prediction of Buoyant Flows in a Cavity Containing an Internal Heat Source [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro
abstract

Buoyancy-induced circulations in a 2D cavity containing rectangular heat source, are predicted numerically. The effect of thermal conditions at the boundaries of cavity is of specific concern. The vertical enclosure walls are in fact isothermal, but different combinations of boundary conditions are admitted at the horizontal walls. These are: isothermal top and bottom walls; top wall isothermal and bottom wall adiabatic; both walls adiabatic. The internal source is isothermal, and air is the working fluid. Results for the three situations are compared for values of the Grashof number, Gr, ranging from 4 x 104 to 4 x 106. The results encompass the stability limit for laminar flow, since a steady-state condition is not obtained at the highest Gr values. It is shown that different thermal boundary conditions give rise to quite different thermal-flow configurations, different heat transfer performances, and, in the high-Gr range, distinctive frequencies of oscillation of the system.

2000 - Enhanced Visualisation of Complex Thermofluid Data: Vertical and Horizontal Combined Convection and Microscale Heat Transfer Cases [Relazione in Atti di Convegno]
Atherton, M. A.; Collins, M. W.; Piva, S.; Barozzi, Giovanni Sebastiano
abstract

In general convective heat transfer is an 'n-dimensional' problem where n is well in excess of 3 for steady flows. Traditionally the method of dimensional analysis results in a small number of dimensionless groups. The first part of the paper revises this subject using sets of data for: a. vertical combined convection in nuclear safety; b. horizontal combined convection review material; c. microchannel heat transfer. The conclusion is reached that heat transfer data are presented in either 'holistic' or 'reductive' modes, and other thermodynamic performance data are realted to the generic scientific cases of (a) 3-D space and (b) multidimensional spacee. In the seconda part of the paper a first attempt is made at applying design-type procedures.

2000 - Natural convection in cavities containing internal sources [Articolo su rivista]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro
abstract

Numerical predictions are reported for buoyan- cy-induced circulations in a 2D closed cavity with internal heat sources. Two cases are considered: (A) two vertical plates with uniform heat generation, forming a short vertical channel within the enclosure; and, (B) a rectangular heating block with uniform wall temperature, placed central in the enclosure. Air, with a Prandtl number 0.71, is considered as the working fluid. The vertical enclosure walls are isothermal, while the horizontal enclosure walls are adiabatic. Results are presented for two values of the Grashof number, one below the stability limit for laminar flow, and one well above it. In those latter cases, the long- term behaviour of the numerical solution is time-dependent, i.e. no steady-state can be reached. Heat transfer results are compared with predictions from standard correlations for isolated surfaces.

2000 - Numerical Study of Time-dependent Buoyancy-induced Cavity Flows [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro
abstract

A 2D square cavity with isothermal horizontal sides and vertical adiabatic sides, is considered, containing a 'virtual' heat source, i.e a heat generating element with permeable boundaries. The horizontal sides of the enclosure are isothermal, and the vertical sides are adiabatic. The source is also square, its size being 1/100 of the cavity side, and is centred in the cavity.The problem is worked out numerically. The solution method is based on control-volume discretizations of the transport equations and a 2nd order projection scheme for time integration.The analysis is directed to demonstrate the potential of the method in the detection of critical values of the leading parameter, the Grashof number, at which some dramatic change in the flow structure occur. The first critical Gr-value, marking the onset of a time-dependent behaviour, is primarily investigated. Air (Pr = 0.71) is considered as the working fluid. The analysis is performed using 31x31, 61x61, and 121x121 grids.The sensitivity of the solution to 'minor' details is also investigated, by treating the same case, but for a 'real' (i.e. with impermeable walls) heat source.

1999 - Instabilità termiche indotte in ambienti di culto da sistemi di riscaldamento a pannelli radianti a pavimento [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; C., Biagini; Dumas, Antonio; S., Mazzacane
abstract

Si presentano i dati sperimentali di velocità e temperatura dell'aria rilevati all'interno della Chiesa di S. Maria della Pietà in Bologna. Una vasta circolazione convettiva è prodotta dall'impianto di riscaldamento a pannelli radianti a pavimento.

1999 - Numerical Simulation of Time-Dependent Buoyant Flows in a Cavity Containing an Internal Heat Source [Relazione in Atti di Convegno]
Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

A time accurate finite volume method is used to predict the buoyancy-induced circulations promoted by an isothermal rectangular body in a rectangular enclosure containing air. Three values of the leading non dimensional parameter, the Grashof number, are consider, encompassing the stability limit for steady laminar flow. The long term behaviour and the heat transfer performance of the system are discussed

1999 - Numerical investigation of a one-side measurement technique for thermal diffusivity [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; Muscio, Alberto; Tartarini, Paolo
abstract

A modified Angstrom’s method for the measurement of the thermal diffusivity of solid materials is presented, aimed at overcoming the limits of ordinary one-side techniques. The method requires a periodic thermal input, alternating heating and cooling stages, to be supplied to the specimen. The thermal diffusivity is estimated by monitoring the temperature oscillations on the free surface of the specimen.The conditions for which a real three-dimensional test-system can be studied by means of a one-dimensional thermal model are investigated by analytical and numerical methods. The algorithms for the estimate of thermal diffusivity are determined for the one-dimensional thermal system and are verified by numerical simulation. The applicability of the algorithms to multi-dimensional configurations is finally explored.

1999 - Numerical simulation of time-dependent buoyant flows in an enclosed vertical channel [Articolo su rivista]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; E., Nobile
abstract

A time-accurate Finite Volume method is used to investigate the two-dimensional buoyant flow in a closed cabinet containing two vertical heating plates. These are parallel, and form a channel at the centre of the cabinet enclosure. The cases of isothermal plates, and of uniform heat generation within them, are both considered for two values, 1 x 10(5) and 1 x 10(7), of the leading non-dimensional parameter, the Grashof number. Air (Pr = 0.71) is considered as the working fluid. Transient and long term thermal and flow behaviours are investigated. Steady-state solutions are asymptotically found at the lower Gr-value. However, time-dependent long-term solutions are predicted at Gr = 1 x 10(7) .

1999 - Photographic investigation of water droplet impingement and boiling on hot surfaces [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; Muscio, Alberto; Tartarini, Paolo
abstract

The present research is aimed at analyzing the behavior of small water droplets impinging, with different Weber numbers, on hot, non-porous surfaces. An experimental and theoretical study is conducted, focusing on the influence of the Weber number on the cooling effects induced by droplet impingement and evaporation in presence of nucleate boiling. In order to get more insight into the phenomenon, the droplets behavior is monitored by a high-speed video-camera, and the influence of the Weber number on dropwise evaporative cooling is analyzed. In particular, the conditions which determine the onset of nucleate boiling are emphasized, and the solid surface cooling transients are also monitored via infrared thermography.

1999 - Water Droplet Boiling on Hot, Non-Porous Ceramic Surfaces [Articolo su rivista]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; T. R., Maciver; Tartarini, Paolo
abstract

In this study, an experimental research is conducted, analyzing the behavior of small water droplets (from 10 to 50 :l) gentlydeposited (the Weber number is less than 13) on hot, non-porous, ceramic surfaces. In particular, the conditions whichdetermine the onset of nucleate boiling are emphasized, and the solid surface cooling is monitored via infrared thermography.The results, mainly concerning the evaporation time of the droplets and the solid surface transient temperature distribution,provide some insight into the mechanisms of dropwise evaporative cooling in presence of nucleate boiling. The non-intrusive method of infrared thermography is also used to study the peculiar thermal behavior of industrial ceramic surfaces subjected to high heating fluxes. Dropwise evaporation under boiling conditions is showed to be an effective method to cool down even non-uniform-temperature ceramic tiles.

1998 - Temperature and Velocity Distributions in a Church with Floor Heating in Various Seasons [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Dumas, Antonio; S., Mazzacane
abstract

Experiences carried out within a large church in Bologna, Italy, equipped with a floor radiant panels heating plant are presented. High velocity air flows are detected, not compatible with thermal comfort. Experimental data form the basis for understanding and controlling thermal instabilities in tall halls.

1998 - Water droplet boiling on hot, non-porous, ceramic surfaces [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; Corticelli, Mauro Alessandro; T. R., Maciver; Tartarini, Paolo
abstract

An experimental research is conducted analysing the behaviour of small water droplets (10-15 microliters) gently deposited on hot non-porous ceramic surfaces. In particular the conditions determining the onset of nucleate boiling are emphasized, and solid surface cooling is monitored via infrared thermography. The results provide insight into the mechanisms of dropwise evaporative cooling in presence of nucleate boiling. THe non-intrusive method of thermography is also used to study the peculiar thermal behavior of industrial ceramic surfaces subjected to high heat fluxes.

1997 - Modellazione termica del dispositivo di scarico di motori a.c. [Relazione in Atti di Convegno]
Muscio, Alberto; Corticelli, Mauro Alessandro; Barozzi, Giovanni Sebastiano
abstract

Si presenta un modello matematico volto alla previsione delle temperature dei gas e delle temperature di parete di dispositivi di scarico dei gas combusti prodotti da motori ad accensione comandata. Il modello, pur nell'ambito delle forti semplificazioni in esso implicite, consente la previsione del comportamento termico dei condotti di scarico con sufficiente attendibilità, come comprovato da esperienze al banco, eseguite presso il Centro Ricerche FIAT di Orbassano - TO. La tecnica predittiva proposta può consentire un più rapido sviluppo di prototipi dei nuovi sistemi di scarico, atti a meglio soddisfare i limiti di emissione sempre più stringenti proposti dalle normative internazionali.

1995 - Combined convection and wall conduction effects in laminar pipe flow: numerical predictions and experimental validation under uniform wall heating [Articolo su rivista]
S., Piva; Barozzi, Giovanni Sebastiano; M. W., Collins
abstract

Laminar combined convection in horizontal circular ducts is investigated both numerically and experimentally, under uniform wall heating. A series of experiments for the heating of water in a long horizontal copper tube are simulated numerically in order to assess the reliability of the theoretical results. Peripheral and axial wall conduction effects, inherently present in the experiments, are accounted for in the numerical model. The cross validation of experimental and numerical data allows significant conclusions to be reached on conjugate conduction and convection with buoyancy effects in horizontal duct flows. Buoyancy is considered for values of the modified Rayleigh number, Ra-q0, up to 5 . 10(6); the forced convection contribution is considered for two values of the entry Reynolds number, Re-0 = 500 and 1000.

1993 - Combined Convenction and Other Effects in Heat Transfer in Horizontal Flows [Monografia/Trattato scientifico]
Barozzi, Giovanni Sebastiano
abstract

Combined convection in horizontal circular ducts in investigated both theoretically and experimentally. In the analyses account is taken of thermal inlet and conjugated wall-to-fluid effects.

1993 - Comparison of Predictive and Experimental Data for Combined Convection in Horizontal Duct FlowProcs. 'CMEM93 6th Intl. Conf. on Computational Methods and Experimental Measurements', Siena, May 1993, Eds., C.A. Brebbia, and G.M. Carlomagno, Comp. Mech.Publ., Southampton Boston, U.K., Vol.1; 169-182.Computational Methods and Experimental Measurements VI: Sixth International Conference on Computational Methods and Experimental Measurements 93Editore: Computational Mechanics PublicationsISBN 1853122300, 9781853122309 [Relazione in Atti di Convegno]
S., Piva; G., Scarcella; Barozzi, Giovanni Sebastiano; M. W., Collins
abstract

The buoyancy effects on laminar flow of water in a uniformly heated circular duct are investigated experimentally over the range 9x10 E4 - 5x10 E6 of the modified Rayleigh Number, Raq. Preliminary results of a full numerical simulation of the experiment are presented, using the finite-volume FLOW3D code.

1993 - Contribution to the Numerical Simulation of Turbulent Natural Convection in Rectangular Enclosures [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; E., Nobile; A. C. M., Sousa
abstract

Turbulence in high Rayleigh number two dimensional confined free convection is modeled by two k-e formulations. Results are presented for a square cavity with Prandtl number of 0.71 and Rayleigh number ranging from 10 E10 to 10 E12. Also, numerical results and experimental measurements are compared for a 10:1 height-to-width aspect ratio cavity filled with water, and Rayleigh number of 8x10 E10. From the comparisons performed it is apparent that k-e modeling in free convection, although yelding acceptable predictions for several qualtities, tends to overestimate the heat-transfer rate.

1993 - Simulazione numerica di deflussi laminari in regime di convezione mista [Capitolo/Saggio]
Barozzi, Giovanni Sebastiano; S., Piva; M., Voli
abstract

Si riassumono le scelte tecniche di carattere numerico adottate per l'approccio numerico al moto laminare in convezione mista entro condotti orizzontali

1993 - Sviluppo ed applicazione di algoritmi ai volumi finiti ed agli elementi finiti 'control volume based' in problemi di convezione naturale non stazionaria [Capitolo/Saggio]
E., Nobile; G., Pittari; W., Chiesa; Barozzi, Giovanni Sebastiano
abstract

Si descrivono alcuni algoritmi basati sulla discretizzazione delle equazioni di Navier-Stokes con il metodo ai volumi di controllo, con riferimento a casi di convezione naturale non stazionaria

1992 - Physical and Numerical Modelling of a Solar Chimney-based Ventilation System for Buildings [Articolo su rivista]
Barozzi, Giovanni Sebastiano; Imbabi, M. S. E.; Nobile, E.; Sousa, A. C. M.
abstract

THe paper describes an experimental and numerical study to analyze the thermal performance of bio-climatic building prototype in NIgeria. The roof performs as a solar chimney, generating an air flow through the living space if the building to provide cooling. Experimental tests on a 1:12 small-scale model of the prototype are outlined, and the results, both qualitative and quantitative, are used to validate a two-dimensional flow simulation model, in which the steady state conservation equations of mass, momentum and thermal energy are solved using a finite volume formulation. The experimental and numerical results, expressed in terms of temperature and velocity fields, for two different windows geometries are critically evaluated and compared with good agreement.

1991 - An Experimental and Numerical Study of Passive Solar Ventialtion in Buildings [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; M. S., Imbabi; E., Nobile; A. C. M., Sousa
abstract

A new bioclimatic building, featuring an integrated solar chimney roof, provided the ideal prototype for design and construction o a 1/12th scale model building and its micro-climate. Laboratory tests and Computational Fluid Dynamics (CFD) simulations of the model allowed the building's performance to be assessed, and together added valuable physical insight into the performance of the proposed passive solar ventilation system. Experimental results also provided the necessary feedback to develop the numerical model, offering a worthwhile alternative to expensive, time consuming full-scale tests.

1991 - Convective Heat Transfer Coefficients in the Circulation [Articolo su rivista]
Barozzi, Giovanni Sebastiano; Dumas, Antonio
abstract

Convective heat transfer in the vessels of the circulatory system is investigated numerically. In the modeling, account is taken of the non-Newtonian rheological properties of blood and the presence of a cell-depleted plasma layer at the vessel wall. The latter is found to produce a remarkable enhancement of the heat transfer rate in the small vessels, while the effects due to the rheological behavior of blood are comparatively low. A comparison with experimental data available in the open literature is finally attempted.

1991 - Scale Models and CFD Analysis of Air Flow in Passively Ventilated Buildings [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; M. S., Imbabi; E., Nobile; A. C. M., Sousa
abstract

A new bioclimatic building concept based on solar-driven ventilation is analysed through the use of physical and numerical modelling. Measurements are conducted for a 1/12th laboratory scale model designed to replicate the full-scale prototype and its microclimate. Predictions are obtained by employing advanced Computational Fluid Dynamics (CFD) techniques, and the experimental results provide the benchmarking required in the development of the numerical model, which may offer a viable alternative to expensive full-scale tests. The combination of laboratory and computational results gives additional physical insight into the prevailing phenomena determining the ventilation levels, and a first assessment on the feasibility of the concept.

1991 - Small-scale and Numerical Modeling of a Passive Solar Ventialtion System [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; M. S., Imbabi; E., Nobile; A. C. M., Sousa
abstract

An experimental and numerical study is presented, analyzing the performance of a new bioclimatic building, featuring an integrated solar chimney roof. Laboratory tests on a 1/2 scale model building, and Computational Fluid Dynamics (CFD) simulations were performed, aimed to provide the needed predictive tools for the thermal behaviour of the full scale prototype. Experimental measurements and numerical results are compared, and they are in good agreement. The study lends support to the practice of combining Small-Scale Modelling and CFD for the evaluation of energy efficiency and comfort in buildings.

1991 - Thermal Coupling in Laminar Double Pipe Heat Exchangers [Articolo su rivista]
G., Pagliarini; Barozzi, Giovanni Sebastiano
abstract

Thermal interaction between the streams of laminar flow double-pipe heat exchangers is investigated theoretically by accounting for axial conduction along the wall separating the fluids. In a countercurrent arrangement, thermal coupling is demonstrated to have a definite influence on all the more important heat transfer parameters, such as the wall temperature, the heat flux density, the local entropy production rate, and the Nusselt number distributions. The overall performance of the device is considered under a second law point of view, and a complete parametric study is carried out.

1990 - Conjugate Heat Transfer in Forced Convection Cooling of Chip Arrays [Relazione in Atti di Convegno]
Barozzi, Giovanni Sebastiano; E., Nobile
abstract

Conjugate heat transfer is considered for a two dimensional developing laminar flow over heat generating blocks protruding in a parallel plate channel. The blocks simulate IC components on a circuit board.

1990 - Turbulent Buoyant Flows in Enclosures [Relazione in Atti di Convegno]
E., Nobile; A. C. M., Sousa; Barozzi, Giovanni Sebastiano
abstract

A new turbulence model is used in 2D differentially heated vertical cavity.

1989 - Accuracy of Two-Equation Turbulence Modelling in Free Convection [Relazione in Atti di Convegno]
E., Nobile; A. C. M., Sousa; Barozzi, Giovanni Sebastiano
abstract

A novel two-equations turbulence model is presented for the analysis of turbulent natural convection in internal flows. The case of a two-dimensional differentially heated vertical cavity is presented.

1989 - An Efficient Parallel Algorithm for the Numerical Solution of Navier-Stokes Equations Using Fortran Structured Multiprogramming [Relazione in Atti di Convegno]
E., Nobile; T., Russo; Barozzi, Giovanni Sebastiano
abstract

A highly parallelised computer algorithm is presented to solve large large algebraic equation systems by discretisation of Navier-Stokes equations, based on Fortran structured multiprogramming.

1989 - Turbulence Modelling in Confined Natural Convection [Articolo su rivista]
E., Nobile; A. C. M., Sousa; Barozzi, Giovanni Sebastiano
abstract

A novel method is presented for buoyancy-induced turbulent flow within a differentially heated vertical cavity.

1987 - Shading Effect of Eggcrate Devices on Vertical Windows of Arbitrary Orientation [Articolo su rivista]
Barozzi, Giovanni Sebastiano; R., Grossa
abstract

A combination of horizontal and vertical elements forming an eggcrate-type shading system is often used in the architectural design of building facades. An analytical-numerical method is presented to estimate the shadingeffect of such a structure on verticalwindows of arbitrary azimuthal orientation. The effect of reflections from aggregate walls is accounted for in the analysis. Daily and monthly average solar radiation data are presented for shaded windows in Venice (45.40° northen latitude). The effects of the window geometry and the eggcrate projection are discussed.

1986 - I recuperatori di calore aria-aria [Articolo su rivista]
S., Salvigni; Barozzi, Giovanni Sebastiano
abstract

Si passano in rassegna le diverse tecnologie di recupero di calore.

1985 - A method to solve conjugate heat transfer problems: the case of fully developed laminar flow in a pipe [Articolo su rivista]
Barozzi, Giovanni Sebastiano; G., Pagliarini
abstract

A simple fast and general technique combining the superposition principle with a finite element method is proposed to deal with conjugate heat transfer problems. The method is employed to consider the wall conduction effect on heat transfer to fully developed laminar flow through a pipe whose exterior boundary is uniformly heated along a finite length. Results are given for two values of each of the four parameters determining the relative importance of axial conduction: the Péclet number, the wall to fluid conductivity ratio, and the dimensionless thick ness and length of the heated section of the pipe.

1985 - Experimental investigation of combined forced and free convection in horizontal and inclined tubes [Articolo su rivista]
Barozzi, Giovanni Sebastiano; E., Zanchini; M., Mariotti
abstract

The effects of free convection on the laminar flow of water through a circular duct are investigated. Boundary conditions are for essentially constant heat transfer rate longitudinally, and circumferentially uniform wall temperature. The effects of the Reynolds ana Rayleigh numbers on heat transfer are investigated for both horizontal and inclined orientations. The experiment covers the range 200-2300 for the inlet RE-number, and 6,000-70,000 for Ra. The effects of pipe inclination are investigated for the slope angle values over the horizontal ranging between 0° and 60°, with laminar ascending flow.

1984 - Conjugated Heat Transfer in a Circular Duct with Uniform and non-Uniform Wall Thickness [Articolo su rivista]
Barozzi, Giovanni Sebastiano; G., Pagliarini
abstract

The interaction between convection and axial heat conduction along a pipe is analysed assuming third kind boundary conditions at the outer face of the duct. Wall thickness is assumed to be either uniform or having periodic step variations in the axial direction. Axial heat conduction is found to have a definite influence on the heat flux and the Nusselt number distributions. However, the overall heat flux can accurately be predicted by ordinary methods disregarding axial conduction in the wall.

1984 - Experimental Investigation of Coupled Conduction and Laminar Convection in a Circular Tube [Articolo su rivista]
Barozzi, Giovanni Sebastiano; G., Pagliarini
abstract

Wall heat conduction effects on laminar flow heat transfer are experimentally investigated. The steady flow of water through a uniformly heated copper pipe is considered in the experiment, which covers a range of Reynolds numbers from 500 to 1900. The thermal behaviour of the test section is simulated numerically and the influence of conduction along the pipe wall is therefore accounted for in the reduction of the data. Fully developed flow results satisfactorily compare with predictions by a theoretical method previously developed by the authors [Heat Technol. 2,72 (1984)]. Results are also reported for the case where the velocity profile is partially developed at the inlet of the heat transfer section. The combined effects on heat transfer of flow development and of wall axial heat conduction are discussed.

1984 - Indagine sperimentale sullo scambio termico laminare in condotti cilindrici: modellazione dell'apparato mediante tecnica numerica [Articolo su rivista]
Barozzi, Giovanni Sebastiano; G., Pagliarini
abstract

Si presenta la tecnica di modellazione dell'apparato sperimentale impiegato per lo studio dello scambio termico coniugato in condotti. In particolare si illustra il metodo di discretizzazione agli elementi finiti della parete riscaldante, modellata come costituita da due strati coassiali, l'uno generativo e l'altro puramente conduttivo.

1984 - Laminar Heat Transfer Coefficients to Blood flowing in a Circular Duct [Articolo su rivista]
Dumas, Antonio; Barozzi, Giovanni Sebastiano
abstract

Entrance-region heat transfer to blood steadily flowing in a pipe is studied. It is assumed that the non-Newtonian behaviour of blood can be expressed both by the Casson equation and the more complex law suggested by Merrill and Pelletier [J. Appl. Physiol.23, 179–182 (1967)]. The possible presence of a thin cell-free plasma layer at the wall is accounted for. The velocity distribution is determined analytically and a solution of the energy equation is obtained by a finite-difference method, for the two cases: (a) the uniform wall temperature, and (b) the uniform wall heat flux. Results are presented for the yield number Y ( = 2Rτy/σum) = 1, 5, 10 and 20 and the non-dimensional marginal layer thickness D ( = σ/R) = 0,0.0002, 0.01 and 0.1.

1984 - Sharp Entry and Transition Effects for Laminar Combined Convection of Water in Vertical Tubes [Articolo su rivista]
Barozzi, Giovanni Sebastiano; Dumas, Antonio; M. W., Collins
abstract

In previous work the authors showed a sharp entry to have a definite effect on laminar forced convection to water in a vertical circular tube. The study has been extended to situations of strong aiding natural convection, and new experimental data and numerical predictions are reported. The expected entry effect is confirmed, but it is found to be less marked in a strong combined convection field than in the previous forced convection study. The experimental data also include evidence of transition from laminar flow, and a possible criterion of transition is investigated, based on the axial location of minimum local Nusselt number. This is experimental and predictive data for this criterion are compared with the experimental correlation of Lawrence and Chato based on a criterion of temperature fluctuations

1982 - Discussion on P.G.H. Allen, O. Szpiro and M.W. Collins ' Prediction Methods for Entry Length Heat Transfer by Combined Laminar Convection in Horizontal Tubes '. This discussion relates to paper No.33 published in Volume 196, pages 409-415 (Proc. Instn. Mech. Engrs., 196, 1982; 409-415)Proc. Instn. Mech. Engrs., 196, 1982; S55-S59. [Articolo su rivista]
Barozzi, Giovanni Sebastiano
abstract

The paper ' Prediction Methods for Entry Length Heat Transfer by Combined Laminar Convection in Horizontal Tubes' by P.G.H. Allen, O. Szpiro and M.W. Collins (Proc. Instn. Mech. Engrs., 196, 1982; 409-415) is commented

1982 - Influenza delle proprietà reologiche del sangue sulla circolazione; relazione sullo stato delle ricerche condotte presso l'Istituto di Fisica Tecnica di Bologna - Rassegna di Bioingegneria [Articolo su rivista]
S., Salvigni; Barozzi, Giovanni Sebastiano
abstract

Si riassumono le attività di ricerca relative alla reologia del sangue e alla sua influenza sulla circolazione in atto presso l'Istituto di Fisica Tecnica della Facoltà di Ingegneria dell'Università di Bologna

1982 - Sulla convezione laminare forzata in regime di ingresso termico con conduzione assiale lungo il fluido [Articolo su rivista]
Barozzi, Giovanni Sebastiano; Dumas, Antonio
abstract

Si analizza per via numerica lo scambio termico nella regione di ingresso di condotti circolari a riscaldamento uniforme alla parete. Nell'analisi si tiene conto degli effetti di conduzione assiale lungo il fluido.

1982 - The Influence of an Abrupt Convergence on Heat Transfer in Circular Ducts [Articolo su rivista]
Barozzi, Giovanni Sebastiano; Dumas, Antonio; R., Pompoli
abstract

The effect of an abrupt convergence on the local heat transfer coefficient at the entrance of a uniformly heated straight pipe has been investigated. Experiments were carried out with water for Reynolds numbers from 200 to 2000, and for Prandtl numbers 4 and 6. The experimental values of the local Nusselt number are considerably lower than expected and strongly Reynolds number dependent in the region near the inlet, whereas they become comparatively high further downstream. This behaviour is discussed in connection with the hypothesis of the occurrence of a separated flow at the inlet section of the pipe. These and several previous experiments, covering turbulent and transitional flows, have been considered and summarised to obtain a general view of the effect of this geometrical configuration on heat transfer

1981 - Laminar Flow Heat Transfer with Axial Conduction in a Circular Tube: a Finite Difference Solution [Relazione in Atti di Convegno]
Dumas, Antonio; Barozzi, Giovanni Sebastiano
abstract

A finite difference technique is developed for evaluating the rate of heat transfer in the thermal entrance region of ducts with axial conduction. The pipe is assumed to extend from minus to plus infinity, while the velocity profile is fully developed. The boundary condition selected is a uniform heat flux for z greater than or equal to 0, while the wall temperature is kept uniform and equal to its minus infinity value for z less than 0. The results show that axial conduction and heat losses from the unheated section of the pipe significantly affect the temperature profile at the inlet of the heated part lower than the local mixed mean temperatures immediately downstream from the start of the heating. It is found that the performance of this type of heat exchanger can be described by a new parameter as an alternative to the usual Nusselt number.

1980 - Determinazione del lavoro di compressione nelle macchine frigorifere alternative [Articolo su rivista]
Barozzi, Giovanni Sebastiano; R., Pompoli
abstract

Si presentano i risultati sperimentali relativi alla misura del lavoro di compressione in un ciclo frigorifero svolto da freon 21. Il lavoro è svolto su di un impianto frigorifero da laboratorio e il compressore è di tipo alternativo. Si esamina l'esponente dell'adiabatica di compressione e si discutono gli effetti di irreversibilità sul coefficiente economico del ciclo

1979 - Prove sperimentali su di una cabina per unità mobile operante in atmosfera inquinata da pesticidi [Articolo su rivista]
S., Salvigni; Barozzi, Giovanni Sebastiano
abstract

Si presentano gli esiti di rilievi sperimentali del livello di inquinamento prodotto all'interno della cabina pressurizzata di un veicolo per la diffusione di pesticidi in agricoltura

1979 - Sull'influenza del coefficiente di convezione tra fluido termovettore e perete interna nei collettori solari piani [Articolo su rivista]
Barozzi, Giovanni Sebastiano; G., Grazzini
abstract

Si esamina per via analitica il rendimento di collettori solari piani a tubi in funzione delle condizioni di scambio termico entro i condotti e sul lato piastra

1978 - Scambio termico tra fluido termovettore e parete interna nei collettori solari piani [Articolo su rivista]
Barozzi, Giovanni Sebastiano; G., Grazzini
abstract

Si analizza la letteratura pertinente la valutazione teorica o sperimentale dei coefficienti di scambio termico all'interno dei condotti dei collettori piani a tubi e aletta, indicando le migliori correlazioni di calcolo

1978 - Un contributo allo studio della trasmissione del calore nella regione di ingresso termoidraulico in condotti verticali con fluido in moto laminare [Articolo su rivista]
Barozzi, Giovanni Sebastiano; A., Cocchi; Dumas, Antonio; R., Pompoli
abstract

Si presentano dati sperimentali relativi alla determinazione del coefficiente di scambio termico nella regione di ingresso di un condotto circolare uniformemente riscaldato in condizioni di moto laminare. Si analizza in dettaglio l'influenza sullo scambio termico della geometria dell'ingresso a spigolo vivo.

1977 - Considerazioni in merito alla depolverazione per mezzo di campi acustici [Articolo su rivista]
Barozzi, Giovanni Sebastiano
abstract

Si esamina la bibliografia relativa alle tecniche di depolverazione di fumi industriali mediante imposizione di un campo acustico di adeguata frequenza

1977 - La distribuzione dei tempi di permanenza nell'apparato circolatorio [Articolo su rivista]
S., Salvigni; M., Mariotti; Barozzi, Giovanni Sebastiano
abstract

Si analizzano per via analitica i tempi di permanenza del sangue nei vasi dell'apparato circolatorio, tenendo conto del carattere non-newtoniano del sangue

1976 - Criteri di progettazione di cabine per unità mobili operanti in atmosfera inquinata da antiparassitari [Articolo su rivista]
S., Salvigni; Barozzi, Giovanni Sebastiano
abstract

Si presenta un'applicazione di un sistema di condizionamento e protezione dall'inquinamento da pesticidi di cabine per macchine agricole

1976 - Determinazione delle perdite di carico e dei profili di velocità medi nell' apparato circolatorio [Articolo su rivista]
S., Salvigni; M., Mariotti; Barozzi, Giovanni Sebastiano
abstract

Si presentano soluzioni analitiche per i profili di velocità per il moto laminare del sangue in vasi dell'apparato circolatorio, tenendo conto del carattere non newtoniano del sangue e della presenza di uno strato plasmatico alla superficie interna dei vasi.

1974 - Alcuni aspetti tecnici delle centrali termiche a gas metano [Articolo su rivista]
Barozzi, Giovanni Sebastiano; G., Raffellini; E., Valdiserri
abstract

Si presentano dati sperimentali sul rumore acustico prodotto da centrali termiche a gas metano.

Università degli studi di Modena e Reggio Emilia

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