Publications Scientifiques

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Author: search.filters.author.Laouar-Meftah, Siham

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    Numerical analysis of gray gas radiation effects on heat and mass transfer in an annular cavity
    (Serbian Society of Heat Transfer Engineers, 2024) Boussandel, Abdelaziz; Laouar-Meftah, Siham; Retiel, Noureddine
    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 thermal radiation reduces the total heat transfer in the annular space regardless of the configuration of the boundary conditions
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    Wall temperature difference effects on coupled double-Diffusive Natural Convection to Radiation in a square cavity
    (2022) Laouar-Meftah, Siham; Lemonnier, D.; Laouti, A.
    In this paper, we study numerically the effect of wall temperature difference on the interaction between gas radiation and double-diffusive natural convection in a square cavity filled with a non-grey air-H2O mixture, at a 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 radiative source term (in the energy equation) is evaluated by the Discrete Ordinates Method associated with the SLW spectral model of Denison and Webb. Results obtained, in aiding flow case, show that at slight walls temperature difference (ΔT= 10°C), gas radiation influences only thermal field. For a higher value (ΔT=50°C), even dynamic and concentration fields are affected. Under the gas radiation effect, convective and total heat transfers are weakened, while the mass transfer is practically insensitive.
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    Impact of wall temperature difference on heat and mass transfers in gray and non-gray gas mixtures
    (Taylor and Francis, 2022) Laouar-Meftah, Siham; Lemonnier, Denis; Laouti, Amina
    This study deals with the numerical investigation of the effect of wall temperature difference (DTÞ on heat and mass transfers in a differentially heated square cavity, filled with gas mixtures (air-CO2 or air-H2O) at a fixed average concentration of pollutant (15% CO2 or H2O). The governing equations are solved by a finite-difference method and the prediction of radiative transfer in molecular gases is taken into account by the SLW model of Denison and Webb. The results are graphically displayed and discussed for two values of DT (5 C and 50 C), when the concentration and temperature gradient generate opposing motions. The results obtained with a non-gray gas are also related to those of a gray gas model, in order to investigate if this assumption is appropriate to be used instead of non-gray calculations.
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    Effets des conditions aux limites thermiques sur le transfert de masse et de chaleur dans un mélange de gaz non-gris air-CO2 (Cas aidant)
    (2021) Laouar-Meftah, Siham; Lemonnier, D.; Laouti, A.
    Dans cette étude, nous analysons numériquement les effets des conditions aux limites thermiques sur le transfert de masse et de chaleur dans une cavité différentiellement chauffée remplie d’un mélange air-CO2, dont les propriétés radiatives varient localement en fonction de la température et de la concentration de l’espèce absorbante (CO2). Les parois verticales de la cavité sont maintenues à des concentrations constantes et à différents niveaux de température, de manière à créer un écoulement de double diffusion aidant (forces thermiques et massiques qui coopèrent). Le modèle numérique utilisé est bidimensionnel, laminaire et fondé sur une approche en vorticité - fonction de courant pour la partie dynamique. Le calcul radiatif est effectué par la méthode des ordonnées discrètes avec un modèle spectral de type somme pondérée de gaz gris (modèle SLW de Denison et Webb). Les résultats obtenus, pour des écarts de température ΔT (entre les parois verticales de la cavité) allant de 5°C à 100°C, montrent que le rayonnement des gaz affecte la structure des écoulements et réduit les transferts de chaleur (convectifs et totaux) et de masse. Avec l’augmentation de ΔT, les effets radiatifs observés s’accentuent essentiellement pour les structures des écoulements.
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    Volumetric gas radiation effects on double-diffusive mixed convection
    (Publisher Logo Conference Proceedings, 2020) Benbrik, Abderrahmane; Cherifi, Mohammed; Sahnoune, Khaled; Laouar-Meftah, Siham; Moderres, Mourad
    This work is devoted to studying the effect of volumetric gas radiation on mixed double-diffusive convection in a lid-driven square cavity. The vertical walls are maintained at different uniform temperatures and concentration gradients in cooperating flow. The horizontal walls are thermally insulated and impermeable to mass transfer. All the walls are assumed to be opaque, diffuse and gray. The top wall moves to the right side at a constant velocity. The cavity is filled with gray gas mixture considered as an absorbing, emitting and not scattering medium. The governing flow equations are solved by a finite volume method. The radiative transfer equation is modeled by discrete ordinates method. Results were presented in the form of isotherms, iso-concentrations, velocity profiles and heat and mass transfer for various values of Richardson number (Ri), Buoyancy ration (N) and optical thickness
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    Non-gray gas radiation effect on mixed convection in lid driven square cavity
    (AIP Conference Proceedings, 2016) Cherifi, Mohammed; Benbrik, Abderahmane; Laouar-Meftah, Siham; Lemonnier, Denis
    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 medium using the Planck mean absorption coefficient, and non-gray medium assumption)
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    Interaction of radiation with double-diffusive natural convection in a three-dimensional cubic cavity filled with a non-gray gas mixture in cooperating cases
    (taylor and francis, 2016) Cherifi, M.; Laouar-Meftah, Siham; Benbrik, Abderahmane; Lemonnier, D.; Saury, D.
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    Modelisation of turbulent natural convection in rectangular cavity filled with methane
    (2011) Benbrik, Abderahmane; Khelifi Touhami, M. S.; Sahnoune, K.; Laouar-Meftah, Siham
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    Comparative study of radiative effects on double diffusive convection in nongray Air-CO2 mixtures in cooperating and opposing flow
    (Hindawi Publishing Corporation, 2015) Laouar-Meftah, Siham; Lemonnier, Denis; Saury, Didier; Benbrik, Abderahmane; Cherifi, Mohamed
    This study analyses the effects of nongray gas radiation on double diffusive convection, in a square differentially heated cavity filled with air-CO2 mixtures, 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 CO2 corresponding 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, radiation effects are more important and depend on the nature of the flow regime