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Fabio Gori

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Papers by Fabio Gori

Numerical simulation of modified Trombe-Michel Walls with exergy and energy analysis

International Communications in Heat and Mass Transfer, 2017

Numerical simulations of three configurations of a modified Trombe-Michel Wall (TMW) are carried ... more Numerical simulations of three configurations of a modified Trombe-Michel Wall (TMW) are carried out and the numerical results are employed to carry on the energy and exergy analyses. The three configurations of the modified Trombe-Michel Wall (TMW) investigated are with sharp edges, with rounded edges and with the guided flow. For each configuration and glaze spacing, spanning from 0.1 m up to 0.5 m, the velocity and the mean air temperature in the channel, the heat flux, the exergy gain and the conductive heat transfer through the massive wall are evaluated numerically. The comparison among the three configurations shows that the guided flow presents the highest energy and exergy efficiency.

Influence of the Reynolds number on the instant flow evolution of a turbulent rectangular free jet of air

International Journal of Heat and Fluid Flow, 2014

The paper is aimed at investigating the influence of the Reynolds number on the instant flow evol... more The paper is aimed at investigating the influence of the Reynolds number on the instant flow evolution of a rectangular free jet of air in the range of Reynolds numbers from Re = 35,300 to Re = 2,200, where the Reynolds number, Re, is defined according to the hydraulic diameter, D, of a rectangular slot of height H, equal to about D = 2H. The Particle Image Velocimetry (PIV) technique allows obtaining the instant PIV visualizations on the central symmetry section of the rectangular jet. The visual inspection of the instant frames with one and two vortices, except for Re = 35,300 where only one vortex images are detected, shows that after the jet exit

Experimental and Numerical Heat Transfer on a Cylinder Cooled by Two Rectangular Jets of Different Heights

Volume 7: Fluids and Heat Transfer, Parts A, B, C, and D, 2012

ABSTRACT The present paper presents experimental measurements of heat transfer on a cylinder, coo... more ABSTRACT The present paper presents experimental measurements of heat transfer on a cylinder, cooled by two rectangular jets of the same width but different height, H, in order to investigate the influence of the jet height on the local and the average cooling rates, because one of the problems in the heat transfer with jet flow is the convenience to choose the height of the jet in comparison to the height of the impinged object. The cylinder, heated by electric current, is set at several distances from the jet exit, x, on the symmetrical plane of symmetry, i.e. in a two-dimensional geometry, in order to find the optimal position which realizes the maximum heat transfer. The experimental heat transfer on the impingement shows that the local Nusselt number, defined with the cylinder diameter, D, is greater for the smaller slot because velocity is slightly higher but the average Nusselt numbers, defined with the cylinder diameter, D, are quite similar because the higher slot has a greater surface of impingement. Local and average Nusselt numbers are in qualitative agreement only if are compared with the same dimensionless distance, x/H, which can be interpreted as the ratio Rex/ReH, which is per unit of mass flow rate or is independent of the mass flow rate. Numerical simulations are carried out with a two-equations turbulent model using the RNG k-ε approach, on a cylinder with the same thickness of the experiments or without thickness. The numerical simulations of the cylinder without thickness are in acceptable agreement for what concern the average Nusselt numbers. The local Nusselt numbers are in fair agreement only if the cylinder has the thickness of the experiments, independently of the heat flow conditions, i.e. uniformly throughout the thickness or from the inner surface.

Heat transfer to air between parallel plates - On the effects of heat conduction in the walls and in the fluid

Heat transfer to air in mechanically fully developed turbulent flow between two parallel plates i... more Heat transfer to air in mechanically fully developed turbulent flow between two parallel plates is examined. The conjugated problem of solving the Fourier equation in the walls and the energy equation in the fluid is investigated. Because of the technical applications of aerothermodynamics, two kinds of walls are considered: i.e., metallic and ceramic. The streamwise conductive heat transfer, both in the walls and fluid, and the turbulent streamwise one in the fluid are taken into account and their importance is examined for a wide range of Reynolds number. Symmetric and asymmetric thermal boundary conditions are considered for walls of various thicknesses.

Influence of thermal irreversibilities on work producing systems

Improvement of performance for each organization depends on a variety of factors that the self-mo... more Improvement of performance for each organization depends on a variety of factors that the self-motivated human resources are one of the great importances of them (Khalatbari et al, 2013). This important derive from Peter drucker statement (1993) that argue the 21th century is the knowledge-economy century. In this economy, the human capitals were identified as an essential asset for organizations and the organization's potential toward success, rooted of human's abilities (Jafari et al, 2013). Also, employees as an important and effectiveness factor in the organizations, responsible for his job performance and organization progress; therefore, to achieve the high performance of job employees should be motivated. Thus, motivation encourages and inspires employee to do their best work in achieving organization goal (Mazlomi et al, 2013).

Zero-Dimensional Unsteady Internal Ballistic Modeling

International Journal of Energetic Materials and Chemical Propulsion, 2002

Image-based computational fluid dynamics in a carotid artery

Literature presents numerical simulations on image-based geometry where blood is treated as a New... more Literature presents numerical simulations on image-based geometry where blood is treated as a Newtonian fluid, while others simulations assumed a non-Newtonian blood with two or three-dimensional axisymmetric geometry. The present work investigates the non-Newtonian behavior of a pulsating blood flow through a stenosed carotid artery, realistically reconstructed with the patient-specific geometry of a 60 years old man with an intimal thickening of 90% degree of stenosis. Lumen boundary contours are segmented using commercial image-processing software AMIRA for a 3D geometry reconstruction. High-quality tetrahedral mesh is generated using commercial mesh-generator code GAMBIT. The 3-D unsteady incompressible Navier-Stokes equations are solved using the commercial finite volume code FLUENT. The boundary condition is assumed from a flow-rate-wave of the literature using the FFT method and imposing a pressure sinusoidal signal with 20 harmonics.

Numerical Prediction of Heat Transfer to Low-Prandtl-Number Fluids

Numerical Heat Transfer, Part B: Fundamentals, 1979

Numerical prediction of the heat transfer to low-Prandtl-number fluids has been carried out. A on... more Numerical prediction of the heat transfer to low-Prandtl-number fluids has been carried out. A one-equation (k) turbulence model in the near-wall region and a two-equation (k ∼ e) turbulence model In the core region are employed. Many expressions proposed in the literature for the Prt numbers are examined. The fully developed temperature profiles obtained are compared with experimental results In the ranges

Microwave Heating of Porous Media

Journal of Heat Transfer, 1987

... ASME (American Society of Mechanical Engineers), Series C); (United States); Journal Volume: ... more

Is Laminar Flow in a Cylindrical Container With a Rotating Cover a Batchelor or Stewartson-Type Solution?

Journal of Fluids Engineering, 1985

Le type de solution depend de la vitesse de rotation du couvercle et de la distance entre le fond... more

Laminar Flow in a Cylindrical Container With a Rotating Cover

Journal of Fluids Engineering, 1982

Unsteady and steady flow in a cylindrical chamber with a rotating cover has been studied for two ... more Unsteady and steady flow in a cylindrical chamber with a rotating cover has been studied for two Reynolds numbers and three aspect ratio values. The structure of the velocity and pressure fields in the apparatus is described. Primary and secondary volumetric flow rates and torque coefficients are also calculated for all six cases solved.

On a New Passive Scalar Equation With Variable Mass Diffusivity: Flow Between Parallel Plates

Journal of Fluids Engineering, 2010

The present work investigates mass conservation equations in turbulent flow between parallel plat... more The present work investigates mass conservation equations in turbulent flow between parallel plates with variable mass diffusivity. Species conservation equations are relative to the average concentration, as well as to the concentration variance. The product of fluctuating mass diffusivity and space gradient of concentration fluctuation is appearing in the equation of mean and concentration variance. A physical interpretation is given to the different terms. The assumption of a relation between mass diffusivity and concentration allows writing expressions for average and fluctuating mass diffusivity, which can be simplified on the basis of theoretical considerations. The new mass flux is expressed as a function of mass diffusivity and a gradient of concentration variance. Further considerations make it possible to model the new terms appearing in the concentration variance equation. The mass conservation equation can be solved when coupled to the equation of concentration variance....

Natural Convection along a Vertical Thin Cylinder with Uniform and Constant Wall Heat Flux

International Journal of Thermophysics, 2006

A theoretical investigation is carried out to study natural convection around a vertical thin cyl... more A theoretical investigation is carried out to study natural convection around a vertical thin cylinder, or a needle, heated at uniform and constant wall heat flux in order to compare the analytical solutions of the present work with previous experimental results. The local non-similarity solution with the first level of truncation, proposed by Minkowycz and Sparrow, is used. The temperature and velocity distributions are calculated for fluids with several Prandtl numbers. The analytical solutions of this work are compared to experimental results carried out with needles of diameters ranging from 0.6 to 1.5 mm and fluids with Prandtl numbers in the range Pr = 0.7-730. The agreement is reasonable good.

Entropy parameters for heat exchanger design

International Journal of Heat and Mass Transfer, 1988

A general expression for entropy generation in counter-current heat exchangers is developed. It i... more A general expression for entropy generation in counter-current heat exchangers is developed. It is applicable to incompressible liquids and perfect gases. Two new entropy generation numbers are defined, NM and NQ. The analysis is applied to an air-air counter-current heat exchanger. The three entropy generation numbers, NS, NM and NQ, have a different variation with NTU at the various values of the capacity flow rate ratio employed in the calculations.

Flow evolution of a turbulent submerged two-dimensional rectangular free jet of air. Average Particle Image Velocimetry (PIV) visualizations and measurements

International Journal of Heat and Fluid Flow, 2013

Two new differential equations of turbulent dissipation rate and apparent viscosity for non-newtonian fluids

International Communications in Heat and Mass Transfer, 2011

A new equation for the dissipation rate of turbulent kinetic energy is derived exactly in conserv... more A new equation for the dissipation rate of turbulent kinetic energy is derived exactly in conservative form for a Generalized Newtonian Fluid (GNF). The transport equations for mass, momentum, and turbulent kinetic energy are written along to the transport equation for the shear rate. A new transport equation for the apparent viscosity is derived assuming the viscosity as dependent only on the shear rate. The assumption is of incompressible two-dimensional GNF flow.

Experimental measurements and theoretical predictions of the thermal conductivity of two phases glass beads

International Communications in Heat and Mass Transfer, 2001

Effective thermal conductivities of dry and water saturated glass beads have been measured with t... more Effective thermal conductivities of dry and water saturated glass beads have been measured with the transient thermal probe method. The glass beads used in the experiments have particles with diameters ranging from 0.07 mm to 6 mm. The thermal probe used for the measurements has au external diameter of 1.2 mm. The effective thermal conductivities of dry and water saturated glass beads, with diameters smaller than 1.2 mm, are well predicted by a theoretical model, proposed by the first author, which uses the experimentally measured porosity. If the diameter of the glass beads is 3 and 6 mm, i.e. it is higher than the probe one; the porosity.of the porous medium is higher near the probe than in the core of the medium. The effective thermal conductivity of the porous medium is then lower because air and water have a lower thermal conductivity thau the solid particles of the beads. A theoretical approach has been used in order to take into account the increase of porosity near the probe. The theoretical models use the corrected porosity, which account for the probe presence, and provide good agreement with the experimental measurements.

A three dimensional exact equation for the turbulent dissipation rate of Generalised Newtonian Fluids

International Communications in Heat and Mass Transfer, 2012

The Flow of inelastic Non-Newtonian fluids is involved in many biological and industrial applicat... more The Flow of inelastic Non-Newtonian fluids is involved in many biological and industrial applications like nanofluids. Despite many years have passed since the beginning of the study of turbulent Non-Newtonian fluids, most of the studies carried out focus the attention on viscoelastic-fluids. In order to make accurate and low-cost prediction on turbulent inelastic Non-Newtonian fluids flow, a RANS Generalized Newtonian Fluid (GNF) turbulence model is required based on exact transport equation of turbulent variables. In a previous paper [52] we achieved the exact transport equations for turbulent kinetic energy and dissipation rate through the introduction of an apparent viscosity transport equation in 2D case for sake of simplicity. The object of this paper is to extend the results given in [52] in 3D case giving the full mathematical demonstration of the exact-equations. The modelling of the unknown terms it is left for a future work.

Experimental thermal diffusivities/conductivities of frozen media through stefan problem simulation

Experimental Thermal and Fluid Science, 1988

1An experimental apparatus to perform soil-freezing experiments on liquidsand systems is describe... more 1An experimental apparatus to perform soil-freezing experiments on liquidsand systems is described. Temperature measurements along the specimen are carried out during the freezing, and the liquid content distribution is measured with the gravimetric method at the end of the process. Water and tert-amyl alcohol are used as liquids in the saturated sand. A liquid layer is maintained on top of the sand to provide a liquid reservoir. Some experiments have been done to reproduce the "Stefan problem." From the relation between freezing front penetration and time, the thermal diffusivity has been evaluated. The thermal conductivity obtained is in agreement with the measurements performed on the same sand with the transient thermal probe method.

Theoretical prediction of thermal conductivity for thermal protection systems

Applied Thermal Engineering, 2012

The present work is aimed to evaluate the effective thermal conductivity of an ablative composite... more The present work is aimed to evaluate the effective thermal conductivity of an ablative composite material in the state of virgin material and in three paths of degradation. The composite material is undergoing ablation with formation of void pores or char and void pores. The one dimensional effective thermal conductivity is evaluated theoretically by the solution of heat conduction under two assumptions, i.e. parallel isotherms and parallel heat fluxes. The paper presents the theoretical model applied to an elementary cubic cell of the composite material which is made of two crossed fibres and a matrix. A numerical simulation is carried out to compare the numerical results with the theoretical ones for different values of the filler volume fraction.

Numerical simulation of modified Trombe-Michel Walls with exergy and energy analysis

International Communications in Heat and Mass Transfer, 2017

Numerical simulations of three configurations of a modified Trombe-Michel Wall (TMW) are carried ... more Numerical simulations of three configurations of a modified Trombe-Michel Wall (TMW) are carried out and the numerical results are employed to carry on the energy and exergy analyses. The three configurations of the modified Trombe-Michel Wall (TMW) investigated are with sharp edges, with rounded edges and with the guided flow. For each configuration and glaze spacing, spanning from 0.1 m up to 0.5 m, the velocity and the mean air temperature in the channel, the heat flux, the exergy gain and the conductive heat transfer through the massive wall are evaluated numerically. The comparison among the three configurations shows that the guided flow presents the highest energy and exergy efficiency.

Influence of the Reynolds number on the instant flow evolution of a turbulent rectangular free jet of air

International Journal of Heat and Fluid Flow, 2014

The paper is aimed at investigating the influence of the Reynolds number on the instant flow evol... more The paper is aimed at investigating the influence of the Reynolds number on the instant flow evolution of a rectangular free jet of air in the range of Reynolds numbers from Re = 35,300 to Re = 2,200, where the Reynolds number, Re, is defined according to the hydraulic diameter, D, of a rectangular slot of height H, equal to about D = 2H. The Particle Image Velocimetry (PIV) technique allows obtaining the instant PIV visualizations on the central symmetry section of the rectangular jet. The visual inspection of the instant frames with one and two vortices, except for Re = 35,300 where only one vortex images are detected, shows that after the jet exit

Experimental and Numerical Heat Transfer on a Cylinder Cooled by Two Rectangular Jets of Different Heights

Volume 7: Fluids and Heat Transfer, Parts A, B, C, and D, 2012

ABSTRACT The present paper presents experimental measurements of heat transfer on a cylinder, coo... more ABSTRACT The present paper presents experimental measurements of heat transfer on a cylinder, cooled by two rectangular jets of the same width but different height, H, in order to investigate the influence of the jet height on the local and the average cooling rates, because one of the problems in the heat transfer with jet flow is the convenience to choose the height of the jet in comparison to the height of the impinged object. The cylinder, heated by electric current, is set at several distances from the jet exit, x, on the symmetrical plane of symmetry, i.e. in a two-dimensional geometry, in order to find the optimal position which realizes the maximum heat transfer. The experimental heat transfer on the impingement shows that the local Nusselt number, defined with the cylinder diameter, D, is greater for the smaller slot because velocity is slightly higher but the average Nusselt numbers, defined with the cylinder diameter, D, are quite similar because the higher slot has a greater surface of impingement. Local and average Nusselt numbers are in qualitative agreement only if are compared with the same dimensionless distance, x/H, which can be interpreted as the ratio Rex/ReH, which is per unit of mass flow rate or is independent of the mass flow rate. Numerical simulations are carried out with a two-equations turbulent model using the RNG k-ε approach, on a cylinder with the same thickness of the experiments or without thickness. The numerical simulations of the cylinder without thickness are in acceptable agreement for what concern the average Nusselt numbers. The local Nusselt numbers are in fair agreement only if the cylinder has the thickness of the experiments, independently of the heat flow conditions, i.e. uniformly throughout the thickness or from the inner surface.

Heat transfer to air between parallel plates - On the effects of heat conduction in the walls and in the fluid

Heat transfer to air in mechanically fully developed turbulent flow between two parallel plates i... more Heat transfer to air in mechanically fully developed turbulent flow between two parallel plates is examined. The conjugated problem of solving the Fourier equation in the walls and the energy equation in the fluid is investigated. Because of the technical applications of aerothermodynamics, two kinds of walls are considered: i.e., metallic and ceramic. The streamwise conductive heat transfer, both in the walls and fluid, and the turbulent streamwise one in the fluid are taken into account and their importance is examined for a wide range of Reynolds number. Symmetric and asymmetric thermal boundary conditions are considered for walls of various thicknesses.

Influence of thermal irreversibilities on work producing systems

Improvement of performance for each organization depends on a variety of factors that the self-mo... more Improvement of performance for each organization depends on a variety of factors that the self-motivated human resources are one of the great importances of them (Khalatbari et al, 2013). This important derive from Peter drucker statement (1993) that argue the 21th century is the knowledge-economy century. In this economy, the human capitals were identified as an essential asset for organizations and the organization's potential toward success, rooted of human's abilities (Jafari et al, 2013). Also, employees as an important and effectiveness factor in the organizations, responsible for his job performance and organization progress; therefore, to achieve the high performance of job employees should be motivated. Thus, motivation encourages and inspires employee to do their best work in achieving organization goal (Mazlomi et al, 2013).

Zero-Dimensional Unsteady Internal Ballistic Modeling

International Journal of Energetic Materials and Chemical Propulsion, 2002

Image-based computational fluid dynamics in a carotid artery

Literature presents numerical simulations on image-based geometry where blood is treated as a New... more Literature presents numerical simulations on image-based geometry where blood is treated as a Newtonian fluid, while others simulations assumed a non-Newtonian blood with two or three-dimensional axisymmetric geometry. The present work investigates the non-Newtonian behavior of a pulsating blood flow through a stenosed carotid artery, realistically reconstructed with the patient-specific geometry of a 60 years old man with an intimal thickening of 90% degree of stenosis. Lumen boundary contours are segmented using commercial image-processing software AMIRA for a 3D geometry reconstruction. High-quality tetrahedral mesh is generated using commercial mesh-generator code GAMBIT. The 3-D unsteady incompressible Navier-Stokes equations are solved using the commercial finite volume code FLUENT. The boundary condition is assumed from a flow-rate-wave of the literature using the FFT method and imposing a pressure sinusoidal signal with 20 harmonics.

Numerical Prediction of Heat Transfer to Low-Prandtl-Number Fluids

Numerical Heat Transfer, Part B: Fundamentals, 1979

Numerical prediction of the heat transfer to low-Prandtl-number fluids has been carried out. A on... more Numerical prediction of the heat transfer to low-Prandtl-number fluids has been carried out. A one-equation (k) turbulence model in the near-wall region and a two-equation (k ∼ e) turbulence model In the core region are employed. Many expressions proposed in the literature for the Prt numbers are examined. The fully developed temperature profiles obtained are compared with experimental results In the ranges

Microwave Heating of Porous Media

Journal of Heat Transfer, 1987

... ASME (American Society of Mechanical Engineers), Series C); (United States); Journal Volume: ... more

Is Laminar Flow in a Cylindrical Container With a Rotating Cover a Batchelor or Stewartson-Type Solution?

Journal of Fluids Engineering, 1985

Le type de solution depend de la vitesse de rotation du couvercle et de la distance entre le fond... more

Laminar Flow in a Cylindrical Container With a Rotating Cover

Journal of Fluids Engineering, 1982

Unsteady and steady flow in a cylindrical chamber with a rotating cover has been studied for two ... more Unsteady and steady flow in a cylindrical chamber with a rotating cover has been studied for two Reynolds numbers and three aspect ratio values. The structure of the velocity and pressure fields in the apparatus is described. Primary and secondary volumetric flow rates and torque coefficients are also calculated for all six cases solved.

On a New Passive Scalar Equation With Variable Mass Diffusivity: Flow Between Parallel Plates

Journal of Fluids Engineering, 2010

The present work investigates mass conservation equations in turbulent flow between parallel plat... more The present work investigates mass conservation equations in turbulent flow between parallel plates with variable mass diffusivity. Species conservation equations are relative to the average concentration, as well as to the concentration variance. The product of fluctuating mass diffusivity and space gradient of concentration fluctuation is appearing in the equation of mean and concentration variance. A physical interpretation is given to the different terms. The assumption of a relation between mass diffusivity and concentration allows writing expressions for average and fluctuating mass diffusivity, which can be simplified on the basis of theoretical considerations. The new mass flux is expressed as a function of mass diffusivity and a gradient of concentration variance. Further considerations make it possible to model the new terms appearing in the concentration variance equation. The mass conservation equation can be solved when coupled to the equation of concentration variance....

Natural Convection along a Vertical Thin Cylinder with Uniform and Constant Wall Heat Flux

International Journal of Thermophysics, 2006

A theoretical investigation is carried out to study natural convection around a vertical thin cyl... more A theoretical investigation is carried out to study natural convection around a vertical thin cylinder, or a needle, heated at uniform and constant wall heat flux in order to compare the analytical solutions of the present work with previous experimental results. The local non-similarity solution with the first level of truncation, proposed by Minkowycz and Sparrow, is used. The temperature and velocity distributions are calculated for fluids with several Prandtl numbers. The analytical solutions of this work are compared to experimental results carried out with needles of diameters ranging from 0.6 to 1.5 mm and fluids with Prandtl numbers in the range Pr = 0.7-730. The agreement is reasonable good.

Entropy parameters for heat exchanger design

International Journal of Heat and Mass Transfer, 1988

A general expression for entropy generation in counter-current heat exchangers is developed. It i... more A general expression for entropy generation in counter-current heat exchangers is developed. It is applicable to incompressible liquids and perfect gases. Two new entropy generation numbers are defined, NM and NQ. The analysis is applied to an air-air counter-current heat exchanger. The three entropy generation numbers, NS, NM and NQ, have a different variation with NTU at the various values of the capacity flow rate ratio employed in the calculations.

Flow evolution of a turbulent submerged two-dimensional rectangular free jet of air. Average Particle Image Velocimetry (PIV) visualizations and measurements

International Journal of Heat and Fluid Flow, 2013

Two new differential equations of turbulent dissipation rate and apparent viscosity for non-newtonian fluids

International Communications in Heat and Mass Transfer, 2011

A new equation for the dissipation rate of turbulent kinetic energy is derived exactly in conserv... more A new equation for the dissipation rate of turbulent kinetic energy is derived exactly in conservative form for a Generalized Newtonian Fluid (GNF). The transport equations for mass, momentum, and turbulent kinetic energy are written along to the transport equation for the shear rate. A new transport equation for the apparent viscosity is derived assuming the viscosity as dependent only on the shear rate. The assumption is of incompressible two-dimensional GNF flow.

Experimental measurements and theoretical predictions of the thermal conductivity of two phases glass beads

International Communications in Heat and Mass Transfer, 2001

Effective thermal conductivities of dry and water saturated glass beads have been measured with t... more Effective thermal conductivities of dry and water saturated glass beads have been measured with the transient thermal probe method. The glass beads used in the experiments have particles with diameters ranging from 0.07 mm to 6 mm. The thermal probe used for the measurements has au external diameter of 1.2 mm. The effective thermal conductivities of dry and water saturated glass beads, with diameters smaller than 1.2 mm, are well predicted by a theoretical model, proposed by the first author, which uses the experimentally measured porosity. If the diameter of the glass beads is 3 and 6 mm, i.e. it is higher than the probe one; the porosity.of the porous medium is higher near the probe than in the core of the medium. The effective thermal conductivity of the porous medium is then lower because air and water have a lower thermal conductivity thau the solid particles of the beads. A theoretical approach has been used in order to take into account the increase of porosity near the probe. The theoretical models use the corrected porosity, which account for the probe presence, and provide good agreement with the experimental measurements.

A three dimensional exact equation for the turbulent dissipation rate of Generalised Newtonian Fluids

International Communications in Heat and Mass Transfer, 2012

The Flow of inelastic Non-Newtonian fluids is involved in many biological and industrial applicat... more The Flow of inelastic Non-Newtonian fluids is involved in many biological and industrial applications like nanofluids. Despite many years have passed since the beginning of the study of turbulent Non-Newtonian fluids, most of the studies carried out focus the attention on viscoelastic-fluids. In order to make accurate and low-cost prediction on turbulent inelastic Non-Newtonian fluids flow, a RANS Generalized Newtonian Fluid (GNF) turbulence model is required based on exact transport equation of turbulent variables. In a previous paper [52] we achieved the exact transport equations for turbulent kinetic energy and dissipation rate through the introduction of an apparent viscosity transport equation in 2D case for sake of simplicity. The object of this paper is to extend the results given in [52] in 3D case giving the full mathematical demonstration of the exact-equations. The modelling of the unknown terms it is left for a future work.

Experimental thermal diffusivities/conductivities of frozen media through stefan problem simulation

Experimental Thermal and Fluid Science, 1988

1An experimental apparatus to perform soil-freezing experiments on liquidsand systems is describe... more 1An experimental apparatus to perform soil-freezing experiments on liquidsand systems is described. Temperature measurements along the specimen are carried out during the freezing, and the liquid content distribution is measured with the gravimetric method at the end of the process. Water and tert-amyl alcohol are used as liquids in the saturated sand. A liquid layer is maintained on top of the sand to provide a liquid reservoir. Some experiments have been done to reproduce the "Stefan problem." From the relation between freezing front penetration and time, the thermal diffusivity has been evaluated. The thermal conductivity obtained is in agreement with the measurements performed on the same sand with the transient thermal probe method.

Theoretical prediction of thermal conductivity for thermal protection systems

Applied Thermal Engineering, 2012

The present work is aimed to evaluate the effective thermal conductivity of an ablative composite... more The present work is aimed to evaluate the effective thermal conductivity of an ablative composite material in the state of virgin material and in three paths of degradation. The composite material is undergoing ablation with formation of void pores or char and void pores. The one dimensional effective thermal conductivity is evaluated theoretically by the solution of heat conduction under two assumptions, i.e. parallel isotherms and parallel heat fluxes. The paper presents the theoretical model applied to an elementary cubic cell of the composite material which is made of two crossed fibres and a matrix. A numerical simulation is carried out to compare the numerical results with the theoretical ones for different values of the filler volume fraction.