siham laouar - Academia.edu (original) (raw)
Papers by siham laouar
Thermal Science
This study deals with a numerical investigation of coupled double diffusive natural convection wi... more This study deals with a numerical investigation of coupled double diffusive natural convection with thermal radiation in an annular cavity containing a gray gas mixture. The black vertical cylindrical walls are maintained at different temperatures and concentrations to create cooperating flows. The finite volume method (using the SIMPLER algorithm) is used to solve the governing equations and the discrete ordinate method (with S8 quadrature) to treat the radiative aspect of the problem. A parametric study illustrating the influence of the optical thickness and the ratio of buoyancy forces, on the flow field and heat and mass transfer for Reyleigh number equal to 5 106 and aspect ratio equal to 1, is performed. The numerical results show that gas radiation modifies the flow structure and the distribution of temperature and concentration in the cavity. The effect of permutation of boundary conditions, between the vertical walls, on heat and mass transfer is also considered. The therma...
Numerical Heat Transfer Part A-applications, Nov 17, 2022
138 p. : ill. ; 30 cmLe but de ce travail est d’étudier numériquement, en régime stationnaire, l’... more 138 p. : ill. ; 30 cmLe but de ce travail est d’étudier numériquement, en régime stationnaire, l’effet du rayonnement de gaz réels sur la convection naturelle de double diffusion laminaire dans une cavité carrée différentiellement chauffée, remplie d’un mélange gazeux binaire (air-CO2 ou air-H2O). La participation radiative du mélange est prise en compte par le modèle spectral de gaz SLW de Denison et Webb. Les effets du rayonnement sont determinés par comparaison avec le cas de la convection naturelle de double diffusion dans un fluide transparent ayant les mêmes caractéristiques que le mélange, mais de coefficient d’absorption nul. Dans le cas aidant, les résultats montrent que le rayonnement modifie un peu la structure de l’écoulement et perturbe le champ thermique et massique, notamment en inclinant leurs lignes iso-valeurs. Le transfert de chaleur total (nombre de Nusselt) est réduit, mais le transfert de masse (nombre de Sherwood) est peu affecté. Dans le cas opposant, les eff...
A two-dimensional radiation code based on the discrete ordinates method (DOM) coupled with spectr... more A two-dimensional radiation code based on the discrete ordinates method (DOM) coupled with spectral line-based weighted sum of grey gases (SLW) model for radiative heat transfer in non-grey absorbing–emitting media for use in conjunction with a computational fluid dynamics (CFD) code was developed. The code was applied to four different kinds of participating media: two homogeneous and isothermal and two non-homogeneous and nonisothermal cases with a single participating gas (CO2 or H2O). Predictive accuracy of the code is compared with the available results in the literature. Comparisons reveal that the discrete ordinates method (DOM) coupled with SLW model provides accurate solutions for radiative heat fluxes and source terms and can be used with confidence in conjunction with CFD codes.
World Academy of Science, Engineering and Technology, International Journal of Aerospace and Mechanical Engineering, 2016
Numerical Heat Transfer, Part A: Applications, 2015
AIP Conference Proceedings, 2016
A numerical study is performed to investigate the effect of non-gray radiation on mixed convectio... more A numerical study is performed to investigate the effect of non-gray radiation on mixed convection in a vertical two sided lid driven square cavity filled with air-H2O-CO2 gas mixture. The vertical moving walls of the enclosure are maintained at two different but uniform temperatures. The horizontal walls are thermally insulated and considered as adiabatic walls. The governing differential equations are solved by a finite-volume method and the SIMPLE algorithm was adopted to solve the pressure–velocity coupling. The radiative transfer equation (RTE) is solved by the discrete ordinates method (DOM). The spectral line weighted sum of gray gases model (SLW) is used to account for non-gray radiation properties. Simulations are performed in configurations where thermal and shear forces induce cooperating buoyancy forces. Streamlines, isotherms, and Nusselt number are analyzed for three different values of Richardson’s number (from 0.1 to 10) and by considering three different medium (transparent medium, gray m...
Proceeding of Proceedings of CHT-15. 6th International Symposium on ADVANCES IN COMPUTATIONAL HEAT TRANSFER , May 25-29, 2015, Rutgers University, New Brunswick, NJ, USA, 2015
2015 International Conference on Industrial Engineering and Operations Management (IEOM), 2015
A numerical study is performed to investigate the effect of the adiabatic walls emissivity on cou... more A numerical study is performed to investigate the effect of the adiabatic walls emissivity on coupled double diffusive natural convection and gas radiation in a differentially heated square enclosure filled with non-gray air-H2O mixtures in a cooperating case. The vertical walls of the enclosure are maintained at two different but uniform temperatures. The remaining boundaries are thermally insulated and considered as adiabatic walls. These walls are assumed to be opaque, diffuse and gray. Their emissivity is variable (ε=0, 0.1, 0.5 and 1). The governing differential equations are solved by a finite-volume method and the SIMPLE algorithm was adopted to solve the pressure-velocity coupling. The discrete ordinates method (DOM) associated with the spectral line weighted-sum-of-gray-gases (SLW) is used to solve the radiative transfer equation. Simulations are performed in configurations where thermal and concentration gradient induces cooperating buoyancy forces. Results obtained for three average molar fractions of H2O (5%, 10% and 20%). The effects of walls emissivity on the flow and temperature fields and heat transfer rates are analyzed.
Mathematical Problems in Engineering, 2015
This study analyses the effects of nongray gas radiation on double diffusive convection, in a squ... more This study analyses the effects of nongray gas radiation on double diffusive convection, in a square differentially heated cavity filled with air-CO2mixtures, when the buoyancy forces (thermal and mass) are cooperating or opposing. The radiative source term in the energy equation is evaluated by the discrete ordinate method (solving the radiative transfer equation) and the SLW spectral model (accounting for real radiative properties of absorbing species). Here, gas absorption varies with the local temperature and concentration of pollutant, which induces a strong direct coupling between the concentration and thermal fields that would not exist with gray gas. Simulations are performed at different concentrations of CO2corresponding to different flow regimes (thermal, transitional, and mass). Results show the following: (i) in cooperating flow, radiation modifies essentially the heat transfer and the characteristics of temperature and concentration fields; (ii) in opposing flow, radia...
2015 International Conference on Industrial Engineering and Operations Management (IEOM), 2015
In this paper we study the effect of the (mass-to-thermal) buoyancy ratio N on the interaction be... more In this paper we study the effect of the (mass-to-thermal) buoyancy ratio N on the interaction between gas radiation and double diffusive convection in a square cavity filled with a non-gray air-H2O mixtures at constant average concentration of H2O (13%). Uniform temperatures and concentrations are imposed along the vertical walls, while the horizontal walls are assumed to be adiabatic and impermeable to mass transfer. The governing equations are solved by a finite-difference method and the spectral dependency of gas radiative properties is handled by the SLW model of Denison and Webb. The results obtained, in opposing flow case, are graphically displayed for three value of N (-0.15, -0.95 and -1.91) to illustrate the influence of this parameter on concentration, temperature and velocity profiles as well as heat and mass flux. Non-gray results are also compared to gray solutions.
International Journal of Thermal Sciences, 2014
We studied numerically the effects of gas radiation on double-diffusive convection in a square en... more We studied numerically the effects of gas radiation on double-diffusive convection in a square enclosure filled with a non-gray aireH 2 O mixture at different concentrations. Uniform temperatures and concentrations are imposed along the two vertical side walls of the enclosure so as to induce opposing thermal and mass buoyancy forces within the fluid. In this work, the radiative aspect of the problem is treated by the discrete ordinate method (to solve the radiative transfer equation) and the SLW spectral model (to account for the radiative properties of the non-gray mixture). Gas absorption varies with the local concentration of H 2 O, which induces a strong direct coupling between the concentration and thermal fields that otherwise would not exist. Numerical results show that radiative effects on the characteristics of streamline, temperature and concentration fields are important, and depend on the nature of the flow regime (thermal at 5% H 2 O, transitional at 10% and mass at 25%). The total heat transfer is reduced whatever the flow regime and the mass transfer is also affected, outside the thermal flow.
Thermal Science
This study deals with a numerical investigation of coupled double diffusive natural convection wi... more This study deals with a numerical investigation of coupled double diffusive natural convection with thermal radiation in an annular cavity containing a gray gas mixture. The black vertical cylindrical walls are maintained at different temperatures and concentrations to create cooperating flows. The finite volume method (using the SIMPLER algorithm) is used to solve the governing equations and the discrete ordinate method (with S8 quadrature) to treat the radiative aspect of the problem. A parametric study illustrating the influence of the optical thickness and the ratio of buoyancy forces, on the flow field and heat and mass transfer for Reyleigh number equal to 5 106 and aspect ratio equal to 1, is performed. The numerical results show that gas radiation modifies the flow structure and the distribution of temperature and concentration in the cavity. The effect of permutation of boundary conditions, between the vertical walls, on heat and mass transfer is also considered. The therma...
Numerical Heat Transfer Part A-applications, Nov 17, 2022
138 p. : ill. ; 30 cmLe but de ce travail est d’étudier numériquement, en régime stationnaire, l’... more 138 p. : ill. ; 30 cmLe but de ce travail est d’étudier numériquement, en régime stationnaire, l’effet du rayonnement de gaz réels sur la convection naturelle de double diffusion laminaire dans une cavité carrée différentiellement chauffée, remplie d’un mélange gazeux binaire (air-CO2 ou air-H2O). La participation radiative du mélange est prise en compte par le modèle spectral de gaz SLW de Denison et Webb. Les effets du rayonnement sont determinés par comparaison avec le cas de la convection naturelle de double diffusion dans un fluide transparent ayant les mêmes caractéristiques que le mélange, mais de coefficient d’absorption nul. Dans le cas aidant, les résultats montrent que le rayonnement modifie un peu la structure de l’écoulement et perturbe le champ thermique et massique, notamment en inclinant leurs lignes iso-valeurs. Le transfert de chaleur total (nombre de Nusselt) est réduit, mais le transfert de masse (nombre de Sherwood) est peu affecté. Dans le cas opposant, les eff...
A two-dimensional radiation code based on the discrete ordinates method (DOM) coupled with spectr... more A two-dimensional radiation code based on the discrete ordinates method (DOM) coupled with spectral line-based weighted sum of grey gases (SLW) model for radiative heat transfer in non-grey absorbing–emitting media for use in conjunction with a computational fluid dynamics (CFD) code was developed. The code was applied to four different kinds of participating media: two homogeneous and isothermal and two non-homogeneous and nonisothermal cases with a single participating gas (CO2 or H2O). Predictive accuracy of the code is compared with the available results in the literature. Comparisons reveal that the discrete ordinates method (DOM) coupled with SLW model provides accurate solutions for radiative heat fluxes and source terms and can be used with confidence in conjunction with CFD codes.
World Academy of Science, Engineering and Technology, International Journal of Aerospace and Mechanical Engineering, 2016
Numerical Heat Transfer, Part A: Applications, 2015
AIP Conference Proceedings, 2016
A numerical study is performed to investigate the effect of non-gray radiation on mixed convectio... more A numerical study is performed to investigate the effect of non-gray radiation on mixed convection in a vertical two sided lid driven square cavity filled with air-H2O-CO2 gas mixture. The vertical moving walls of the enclosure are maintained at two different but uniform temperatures. The horizontal walls are thermally insulated and considered as adiabatic walls. The governing differential equations are solved by a finite-volume method and the SIMPLE algorithm was adopted to solve the pressure–velocity coupling. The radiative transfer equation (RTE) is solved by the discrete ordinates method (DOM). The spectral line weighted sum of gray gases model (SLW) is used to account for non-gray radiation properties. Simulations are performed in configurations where thermal and shear forces induce cooperating buoyancy forces. Streamlines, isotherms, and Nusselt number are analyzed for three different values of Richardson’s number (from 0.1 to 10) and by considering three different medium (transparent medium, gray m...
Proceeding of Proceedings of CHT-15. 6th International Symposium on ADVANCES IN COMPUTATIONAL HEAT TRANSFER , May 25-29, 2015, Rutgers University, New Brunswick, NJ, USA, 2015
2015 International Conference on Industrial Engineering and Operations Management (IEOM), 2015
A numerical study is performed to investigate the effect of the adiabatic walls emissivity on cou... more A numerical study is performed to investigate the effect of the adiabatic walls emissivity on coupled double diffusive natural convection and gas radiation in a differentially heated square enclosure filled with non-gray air-H2O mixtures in a cooperating case. The vertical walls of the enclosure are maintained at two different but uniform temperatures. The remaining boundaries are thermally insulated and considered as adiabatic walls. These walls are assumed to be opaque, diffuse and gray. Their emissivity is variable (ε=0, 0.1, 0.5 and 1). The governing differential equations are solved by a finite-volume method and the SIMPLE algorithm was adopted to solve the pressure-velocity coupling. The discrete ordinates method (DOM) associated with the spectral line weighted-sum-of-gray-gases (SLW) is used to solve the radiative transfer equation. Simulations are performed in configurations where thermal and concentration gradient induces cooperating buoyancy forces. Results obtained for three average molar fractions of H2O (5%, 10% and 20%). The effects of walls emissivity on the flow and temperature fields and heat transfer rates are analyzed.
Mathematical Problems in Engineering, 2015
This study analyses the effects of nongray gas radiation on double diffusive convection, in a squ... more This study analyses the effects of nongray gas radiation on double diffusive convection, in a square differentially heated cavity filled with air-CO2mixtures, when the buoyancy forces (thermal and mass) are cooperating or opposing. The radiative source term in the energy equation is evaluated by the discrete ordinate method (solving the radiative transfer equation) and the SLW spectral model (accounting for real radiative properties of absorbing species). Here, gas absorption varies with the local temperature and concentration of pollutant, which induces a strong direct coupling between the concentration and thermal fields that would not exist with gray gas. Simulations are performed at different concentrations of CO2corresponding to different flow regimes (thermal, transitional, and mass). Results show the following: (i) in cooperating flow, radiation modifies essentially the heat transfer and the characteristics of temperature and concentration fields; (ii) in opposing flow, radia...
2015 International Conference on Industrial Engineering and Operations Management (IEOM), 2015
In this paper we study the effect of the (mass-to-thermal) buoyancy ratio N on the interaction be... more In this paper we study the effect of the (mass-to-thermal) buoyancy ratio N on the interaction between gas radiation and double diffusive convection in a square cavity filled with a non-gray air-H2O mixtures at constant average concentration of H2O (13%). Uniform temperatures and concentrations are imposed along the vertical walls, while the horizontal walls are assumed to be adiabatic and impermeable to mass transfer. The governing equations are solved by a finite-difference method and the spectral dependency of gas radiative properties is handled by the SLW model of Denison and Webb. The results obtained, in opposing flow case, are graphically displayed for three value of N (-0.15, -0.95 and -1.91) to illustrate the influence of this parameter on concentration, temperature and velocity profiles as well as heat and mass flux. Non-gray results are also compared to gray solutions.
International Journal of Thermal Sciences, 2014
We studied numerically the effects of gas radiation on double-diffusive convection in a square en... more We studied numerically the effects of gas radiation on double-diffusive convection in a square enclosure filled with a non-gray aireH 2 O mixture at different concentrations. Uniform temperatures and concentrations are imposed along the two vertical side walls of the enclosure so as to induce opposing thermal and mass buoyancy forces within the fluid. In this work, the radiative aspect of the problem is treated by the discrete ordinate method (to solve the radiative transfer equation) and the SLW spectral model (to account for the radiative properties of the non-gray mixture). Gas absorption varies with the local concentration of H 2 O, which induces a strong direct coupling between the concentration and thermal fields that otherwise would not exist. Numerical results show that radiative effects on the characteristics of streamline, temperature and concentration fields are important, and depend on the nature of the flow regime (thermal at 5% H 2 O, transitional at 10% and mass at 25%). The total heat transfer is reduced whatever the flow regime and the mass transfer is also affected, outside the thermal flow.