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Mliki B.,Ur Unite Of Recherche Materiaux | Abbassi M.A.,Ur Unite Of Recherche Materiaux | Omri A.,Ur Unite Of Recherche Materiaux | Zeghmati B.,University of Perpignan
Powder Technology | Year: 2016

In this numerical work, natural convection of CuO-water nanofluid and pure water in a cavity submitted to different heating modes on its vertical walls, is analyzed using the Lattice Boltzmann Method (LBM). The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo-Kleinstreuer-Li) correlation. The influence of pertinent parameters such as Rayleigh number (Ra = 103-106), Hartmann number (Ha = 0-80), heat generation or absorption coefficient (q = -10, -5, 0, 5, 10) and nanoparticle volume concentration (φ = 0-0.04) on the flow and heat transfer characteristics has been examined. In general, by considering the role of Brownian motion, the enhancement in heat transfer is observed at any Hartman and Rayleigh numbers. In addition, the heat generation or absorption influences the heat transfer in the cavity at Ra = 103 more than other Rayleigh numbers as the least effect is observed at Ra = 106. © 2016 Elsevier B.V.


Mliki B.,Ur Unite Of Recherche Materiaux | Abbassi M.A.,Ur Unite Of Recherche Materiaux | Omri A.,Ur Unite Of Recherche Materiaux | Zeghmati B.,University of Perpignan
Powder Technology | Year: 2015

In this numerical work, MHD natural convection of Cu-water nanofluid and pure water in a cavity with the left wall being linearly heated is analyzed using the Lattice Boltzmann Method (LBM). The effective thermal conductivity and viscosity of nanofluid are calculated by the Maxwell-Garnetts (MG) and Brinkman models, respectively. The influence of pertinent parameters such as Hartmann number (Ha=0-60), Rayleigh number (Ra=103-106), heat generation or absorption coefficient (q=-10, -5, 0, 5, 10) and nanoparticle volume concentration (ϕ=0-0.05) on the flow and heat transfer characteristics has been examined. The results show that the heat transfer increases with an increase of the Rayleigh number and decreases with an increase of the Hartmann number. In addition, the results show that the heat generation or absorption coefficient has a significant effect on the streamlines, isotherms and vortex formation in the enclosure. Moreover, the increase of nanoparticles volume fraction has a positive impact on the average Nusselt number. © 2015 Elsevier B.V.


Mahmoudi A.,Ur Unite Of Recherche Materiaux | Mejri I.,Ur Unite Of Recherche Materiaux | Abbassi M.A.,Ur Unite Of Recherche Materiaux | Omri A.,Ur Unite Of Recherche Materiaux
Fluid Dynamics and Materials Processing | Year: 2013

A double-population Lattice Boltzmann Method (LBM) is applied to solve the steady-state laminar natural convective heat-transfer problem in a triangular cavity filled with air (Pr = 0.71). Two different boundary conditions are implemented for the vertical and inclined boundaries: Case I) adiabatic vertical wall and inclined isothermal wall, Case II) isothermal vertical wall and adiabatic inclined wall. The bottom wall is assumed to be at a constant temperature (isothermal) for both cases. The buoyancy effect is modeled in the framework of the well-known Boussinesq approximation. The velocity and temperature fields are determined by a D2Q9 LBM and a D2Q4 LBM, respectively. Comparison with previously published work shows excellent agreement. Numerical results are obtained for a wide range of parameters: the Rayleigh number spanning the range (103-106) and the inclination angle varying in the intervals (0° to 120°) and (0° to 360°) for cases I and II, respectively. Flow and thermal fields are given in terms of streamlines and isotherms distributions. It is observed that inclination angle can be used as a relevant parameter to control heat transfer in right-angled triangular enclosures. © 2013 Tech Science Press.


Mejri I.,Ur Unite Of Recherche Materiaux | Mahmoudi A.,Ur Unite Of Recherche Materiaux | Abbassi M.A.,Ur Unite Of Recherche Materiaux | Omri A.,Ur Unite Of Recherche Materiaux
International Journal of Heat and Technology | Year: 2014

This paper examines the natural convection in a square enclosure filled with a water-Al2O3 nanofluid and is subjected to a magnetic field. The side walls of the cavity have spatially varying sinusoidal temperature distributions. The horizontal walls are adiabatic. Lattice Boltzmann method (LBM) is applied to solve the coupled equations of flow and temperature fields. This study has been carried out for the pertinent parameters in the following ranges: Rayleigh number of the base fluid, Ra=103 to 105, Hartmann number varied from Ha=0 to 50, phase deviation (γ=0, π/4, π/2, 3π/4 and π) and the solid volume fraction of the nanoparticles between φ = 0 and 6%. The results show that the heat transfer rate increases with an increase of the Rayleigh number but it decreases with an increase of the Hartmann number. Also it is observed that the Phase deviation control the heat transfer rate.


Mahmoudi A.,Ur Unite Of Recherche Materiaux | Mejri I.,Ur Unite Of Recherche Materiaux | Abbassi M.A.,Ur Unite Of Recherche Materiaux | Omri A.,Ur Unite Of Recherche Materiaux
Powder Technology | Year: 2014

This paper examines the natural convection in a square enclosure filled with a water-Al2O3 nanofluid and is subjected to a magnetic field. The bottom wall is uniformly heated and vertical walls are linearly heated whereas the top wall is well insulated. Lattice Boltzmann Method (LBM) is applied to solve the coupled equations of flow and temperature fields. This study has been carried out for the pertinent parameters in the following ranges: Rayleigh number of the base fluid, Ra=103 to 105, Hartmann number varied from Ha=0 to 60, the inclination angle of the magnetic field relative to the horizontal plane γ=0° to 180° and the solid volume fraction of the nanoparticles between φ=0 and 6%. The results show that the heat transfer rate increases with an increase of the Rayleigh number but it decreases with an increase of the Hartmann number. Also for Ra≥5×104 and for the range of Hartmann number study, we note that the heat transfer and fluid flow depend strongly upon the direction of magnetic field. In addition, according the Hartmann number, it observed that the magnetic field direction controls the effects of nanoparticles. © 2014 Elsevier B.V.

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