Khedidja Bouhadef - Academia.edu (original) (raw)

Papers by Khedidja Bouhadef

International Journal of Thermal Sciences, 2011

ABSTRACT A numerical investigation is performed for heat transfer enhancement in a parallel-plate... more ABSTRACT A numerical investigation is performed for heat transfer enhancement in a parallel-plate channel. Porous blocks are inserted to partially fill the channel, which is crossed by a power-law fluid. The modified Brinkman–Forchheimer extended Darcy model for power-law fluids is used in the porous layer while the Navier–Stokes equation are employed in the clear region of the channel. Results are reported for two cases: (1) a channel with a single porous block and (2) a channel with two porous blocks mounted alternatively at the bottom and top walls of the channel. The combined effects of both the porous blocks and the non-Newtonian fluid properties on the hydrodynamic and thermal characteristics of the flow are analyzed. To this end, computations are performed to highlight the effect of parameters such as the Darcy number, the Reynolds number, and the power-law index. For the case of the single porous block, the heat transfer is enhanced and maximized at low permeability. In the second configuration as well, heat transfer improvement can also be obtained, even if the thermal conductivity ratio is equal to 1. This enhancement is maximized for particular values of the Darcy number that depend on the flow pattern and the power-law index. Concerning the rheological aspect, it is found that pseudo plastic fluids exhibit the highest Nusselt number and the lowest pressure loss. The presence of the porous inserts causes a significant increase in pressure drop, which is found to be more important with dilatant fluids.

Physical Review E, 2013

In this work the instability of the Taylor-Couette flow for Newtonian and non-Newtonian fluids (d... more In this work the instability of the Taylor-Couette flow for Newtonian and non-Newtonian fluids (dilatant and pseudoplastic fluids) is investigated for cases of finite aspect ratios. The study is conducted numerically using the lattice Boltzmann method (LBM). In many industrial applications, the apparatuses and installations drift away from the idealized case of an annulus of infinite length, and thus the end caps effect can no longer be ignored. The inner cylinder is rotating while the outer one and the end walls are maintained at rest. The lattice two-dimensional nine-velocity (D2Q9) Boltzmann model developed from the Bhatnagar-Gross-Krook approximation is used to obtain the flow field for fluids obeying the power-law model. The combined effects of the Reynolds number, the radius ratio, and the power-law index n on the flow characteristics are analyzed for an annular space of finite aspect ratio. Two flow modes are obtained: a primary Couette flow (CF) mode and a secondary Taylor vortex flow (TVF) mode. The flow structures so obtained are different from one mode to another. The critical Reynolds number Re c for the passage from the primary to the secondary mode exhibits the lowest value for the pseudoplastic fluids and the highest value for the dilatant fluids. The findings are useful for studies of the swirling flow of non-Newtonians fluids in axisymmetric geometries using LBM. The flow changes from the CF to TVF and its structure switches from the two-cells to four-cells regime for both Newtonian and dilatant fluids. Contrariwise for pseudoplastic fluids, the flow exhibits 2-4-2 structure passing from two-cells to four cells and switches again to the two-cells configuration. Furthermore, the critical Reynolds number presents a monotonic increase with the power-law index n of the non-Newtonian fluid, and as the radius ratio grows, the transition flow regimes tend to appear for higher critical Reynolds numbers.

International Journal of Numerical Methods for Heat & Fluid Flow, 2006

Purpose – To investigate the forced convection heat transfer to hydrodynamically and thermally fu... more Purpose – To investigate the forced convection heat transfer to hydrodynamically and thermally fully developed laminar steady flow of power-law non-Newtonian fluid in a partially porous square duct. Design/methodology/approach – The modified Brinkmann-Forchheimer extended Darcy model for power-law fluids is used in the porous layer. The solutions for the velocity and temperature fields are obtained numerically using the finite volume

Numerical Heat Transfer Applications

ABSTRACT

Defect and Diffusion Forum, 2010

... 0,1 0,2 0,3 0,4 0,5 0,6 (a) Re=200;Da=10-3;Bint=1;Fkm=100;t=10 Bi=100 Bi=1 Bi=0.01 W a ll T e... more ... 0,1 0,2 0,3 0,4 0,5 0,6 (a) Re=200;Da=10-3;Bint=1;Fkm=100;t=10 Bi=100 Bi=1 Bi=0.01 W a ll T e m p e ra tu re Z Solid Fluid 0,0 0,2 0,4 0,6 0,8 1,0 0,0 0,2 0,4 0,6 0,8 1,0 (b) Re=200;Da=10-3;Bint=1;Fkm=100;t=10 Bi=100 Bi=1 Bi=0.01 W a ll C o n c e n tra tio n Z Solid Fluid ...

Progress in Computational Fluid Dynamics, An International Journal, 2011

ABSTRACT Investigation of the fluids purification process, either by filtration or by undesirable... more ABSTRACT Investigation of the fluids purification process, either by filtration or by undesirable substances destruction, is conducted. A convective flow in a reactive porous medium with an axisymmetrical geometry is considered. The momentum equation for the forced convection through a porous substrate is modelled by using the Darcy-Brinkman-Forchheimer model, while the temperature and the concentration fields are obtained subsequently from the energy and diffusion equations. The effects of the main governing parameters such as solid-to-fluid conductivity ratio, Reynolds number, Biot number, as well as the modified Frank-Kamenetskii number (FK)<sub align="right"> m are studied. The comparison with previously published work shows an excellent agreement.

Journal of Porous Media, 2012

Journal of Applied Sciences, 2008

ABSTRACT

International Journal of Heat and Fluid Flow, Jun 30, 1998

Results are presented for laminar forced convection cooling of heat generating blocks mounted on ... more Results are presented for laminar forced convection cooling of heat generating blocks mounted on a wall in a parallel plate channel. The eect on heat transfer of insertion of a porous matrix between the blocks is considered. The¯ow in the porous medium is modeled using the Brinkman±Forchheimer extended Darcy model. The mass, momentum and energy equations are solved numerically by a control-volume-based procedure. The local Nusselt number at the walls of the blocks, the mean Nusselt numbers and the maximum temperature in the blocks are examined for a wide range of Darcy number and thermal conductivity ratio. The computations are ®rst conducted for a single block, then for evenly mounted blocks. The results show that the insertion of a porous material between the blocks may enhance the heat transfer rate on the vertical sides of the blocks. Although the porous matrix reduces the heat transfer coecient on the horizontal face, signi®cant increases in the mean Nusselt number (up to 50%) are predicted and the maximum temperatures within the heated blocks are reduced in comparison with the pure¯uid case. Ó 1998 Elsevier Science Inc. All rights reserved.

Int J Heat Mass Transfer, 1995

An analytical solution is obtained for a fully developed, forced convection in a gap between two ... more An analytical solution is obtained for a fully developed, forced convection in a gap between two concentric cylinders. The inner is exposed to a constant heat flux and the outer is thermally insulated. A porous layer is attached to the inner cylinder. The effects of the permeability, thermal conductivity and the thickness of the porous material are investigated using a Brinkman+xtended Darcy model. It is shown that there exists a critical thickness of the porous layer at which heat transfer is minimum in the case of low thermal conductivity materials, while this does not show for highly conducting materials. The obtained results show that increasing either the permeability or the thermal conductivity improves the heat transfer. Further, for highly permeable and conducting porous media, it may not be necessary to fill the gap completely to attain the maximum heat transfer.

Arabian Journal for Science and Engineering, 2015

ABSTRACT

Http Dx Doi Org 10 1080 10407789508913770, Oct 29, 2007

... of A. At first, in order to estimate the importance of the inertia term, a critical value of ... more ... of A. At first, in order to estimate the importance of the inertia term, a critical value of CF is defined as being the value at which the Forchheimer term produces a decrease of the flow rate through the annulus by 5% in comparison with the flow rate calculated with the DB model. ...

Journal of Applied Fluid Mechanics

ABSTRACT

Dans cette étude, nous étudions numériquement la convection naturelle instationnaire dans une cav... more Dans cette étude, nous étudions numériquement la convection naturelle instationnaire dans une cavité carrée fermée, dont les parois horizontales sont adiabatiques, et, les parois verticales sont chauffées à la demi-hauteur inferieure ,et refroidies dans leur partie supérieure de la cavité. Nous étudions deux cavités inclinées correspondant à un angle α = 0 et α = 45 degrés .L'écoulement est laminaire et bidimensionnel .Les équations de transfert adimensionnelles exprimées en terme de vorticite et de fonction de courant, ont été résolues avec la méthode implicite des directions alternées à laquelle on a associè la méthode de l'élimination de GAUSS.Nous analysons les effets du nombre de Rayleigh et de l'inclinaison sur les routes vers le chaos qu'emprunte le système.

International Journal of Thermal Sciences, 2011

ABSTRACT A numerical investigation is performed for heat transfer enhancement in a parallel-plate... more ABSTRACT A numerical investigation is performed for heat transfer enhancement in a parallel-plate channel. Porous blocks are inserted to partially fill the channel, which is crossed by a power-law fluid. The modified Brinkman–Forchheimer extended Darcy model for power-law fluids is used in the porous layer while the Navier–Stokes equation are employed in the clear region of the channel. Results are reported for two cases: (1) a channel with a single porous block and (2) a channel with two porous blocks mounted alternatively at the bottom and top walls of the channel. The combined effects of both the porous blocks and the non-Newtonian fluid properties on the hydrodynamic and thermal characteristics of the flow are analyzed. To this end, computations are performed to highlight the effect of parameters such as the Darcy number, the Reynolds number, and the power-law index. For the case of the single porous block, the heat transfer is enhanced and maximized at low permeability. In the second configuration as well, heat transfer improvement can also be obtained, even if the thermal conductivity ratio is equal to 1. This enhancement is maximized for particular values of the Darcy number that depend on the flow pattern and the power-law index. Concerning the rheological aspect, it is found that pseudo plastic fluids exhibit the highest Nusselt number and the lowest pressure loss. The presence of the porous inserts causes a significant increase in pressure drop, which is found to be more important with dilatant fluids.

Physical Review E, 2013

In this work the instability of the Taylor-Couette flow for Newtonian and non-Newtonian fluids (d... more In this work the instability of the Taylor-Couette flow for Newtonian and non-Newtonian fluids (dilatant and pseudoplastic fluids) is investigated for cases of finite aspect ratios. The study is conducted numerically using the lattice Boltzmann method (LBM). In many industrial applications, the apparatuses and installations drift away from the idealized case of an annulus of infinite length, and thus the end caps effect can no longer be ignored. The inner cylinder is rotating while the outer one and the end walls are maintained at rest. The lattice two-dimensional nine-velocity (D2Q9) Boltzmann model developed from the Bhatnagar-Gross-Krook approximation is used to obtain the flow field for fluids obeying the power-law model. The combined effects of the Reynolds number, the radius ratio, and the power-law index n on the flow characteristics are analyzed for an annular space of finite aspect ratio. Two flow modes are obtained: a primary Couette flow (CF) mode and a secondary Taylor vortex flow (TVF) mode. The flow structures so obtained are different from one mode to another. The critical Reynolds number Re c for the passage from the primary to the secondary mode exhibits the lowest value for the pseudoplastic fluids and the highest value for the dilatant fluids. The findings are useful for studies of the swirling flow of non-Newtonians fluids in axisymmetric geometries using LBM. The flow changes from the CF to TVF and its structure switches from the two-cells to four-cells regime for both Newtonian and dilatant fluids. Contrariwise for pseudoplastic fluids, the flow exhibits 2-4-2 structure passing from two-cells to four cells and switches again to the two-cells configuration. Furthermore, the critical Reynolds number presents a monotonic increase with the power-law index n of the non-Newtonian fluid, and as the radius ratio grows, the transition flow regimes tend to appear for higher critical Reynolds numbers.

International Journal of Numerical Methods for Heat & Fluid Flow, 2006

Purpose – To investigate the forced convection heat transfer to hydrodynamically and thermally fu... more Purpose – To investigate the forced convection heat transfer to hydrodynamically and thermally fully developed laminar steady flow of power-law non-Newtonian fluid in a partially porous square duct. Design/methodology/approach – The modified Brinkmann-Forchheimer extended Darcy model for power-law fluids is used in the porous layer. The solutions for the velocity and temperature fields are obtained numerically using the finite volume

Numerical Heat Transfer Applications

ABSTRACT

Defect and Diffusion Forum, 2010

... 0,1 0,2 0,3 0,4 0,5 0,6 (a) Re=200;Da=10-3;Bint=1;Fkm=100;t=10 Bi=100 Bi=1 Bi=0.01 W a ll T e... more ... 0,1 0,2 0,3 0,4 0,5 0,6 (a) Re=200;Da=10-3;Bint=1;Fkm=100;t=10 Bi=100 Bi=1 Bi=0.01 W a ll T e m p e ra tu re Z Solid Fluid 0,0 0,2 0,4 0,6 0,8 1,0 0,0 0,2 0,4 0,6 0,8 1,0 (b) Re=200;Da=10-3;Bint=1;Fkm=100;t=10 Bi=100 Bi=1 Bi=0.01 W a ll C o n c e n tra tio n Z Solid Fluid ...

Progress in Computational Fluid Dynamics, An International Journal, 2011

ABSTRACT Investigation of the fluids purification process, either by filtration or by undesirable... more ABSTRACT Investigation of the fluids purification process, either by filtration or by undesirable substances destruction, is conducted. A convective flow in a reactive porous medium with an axisymmetrical geometry is considered. The momentum equation for the forced convection through a porous substrate is modelled by using the Darcy-Brinkman-Forchheimer model, while the temperature and the concentration fields are obtained subsequently from the energy and diffusion equations. The effects of the main governing parameters such as solid-to-fluid conductivity ratio, Reynolds number, Biot number, as well as the modified Frank-Kamenetskii number (FK)<sub align="right"> m are studied. The comparison with previously published work shows an excellent agreement.

Journal of Porous Media, 2012

Journal of Applied Sciences, 2008

ABSTRACT

International Journal of Heat and Fluid Flow, Jun 30, 1998

Results are presented for laminar forced convection cooling of heat generating blocks mounted on ... more Results are presented for laminar forced convection cooling of heat generating blocks mounted on a wall in a parallel plate channel. The eect on heat transfer of insertion of a porous matrix between the blocks is considered. The¯ow in the porous medium is modeled using the Brinkman±Forchheimer extended Darcy model. The mass, momentum and energy equations are solved numerically by a control-volume-based procedure. The local Nusselt number at the walls of the blocks, the mean Nusselt numbers and the maximum temperature in the blocks are examined for a wide range of Darcy number and thermal conductivity ratio. The computations are ®rst conducted for a single block, then for evenly mounted blocks. The results show that the insertion of a porous material between the blocks may enhance the heat transfer rate on the vertical sides of the blocks. Although the porous matrix reduces the heat transfer coecient on the horizontal face, signi®cant increases in the mean Nusselt number (up to 50%) are predicted and the maximum temperatures within the heated blocks are reduced in comparison with the pure¯uid case. Ó 1998 Elsevier Science Inc. All rights reserved.

Int J Heat Mass Transfer, 1995

An analytical solution is obtained for a fully developed, forced convection in a gap between two ... more An analytical solution is obtained for a fully developed, forced convection in a gap between two concentric cylinders. The inner is exposed to a constant heat flux and the outer is thermally insulated. A porous layer is attached to the inner cylinder. The effects of the permeability, thermal conductivity and the thickness of the porous material are investigated using a Brinkman+xtended Darcy model. It is shown that there exists a critical thickness of the porous layer at which heat transfer is minimum in the case of low thermal conductivity materials, while this does not show for highly conducting materials. The obtained results show that increasing either the permeability or the thermal conductivity improves the heat transfer. Further, for highly permeable and conducting porous media, it may not be necessary to fill the gap completely to attain the maximum heat transfer.

Arabian Journal for Science and Engineering, 2015

ABSTRACT

Http Dx Doi Org 10 1080 10407789508913770, Oct 29, 2007

... of A. At first, in order to estimate the importance of the inertia term, a critical value of ... more ... of A. At first, in order to estimate the importance of the inertia term, a critical value of CF is defined as being the value at which the Forchheimer term produces a decrease of the flow rate through the annulus by 5% in comparison with the flow rate calculated with the DB model. ...

Journal of Applied Fluid Mechanics

ABSTRACT

Dans cette étude, nous étudions numériquement la convection naturelle instationnaire dans une cav... more Dans cette étude, nous étudions numériquement la convection naturelle instationnaire dans une cavité carrée fermée, dont les parois horizontales sont adiabatiques, et, les parois verticales sont chauffées à la demi-hauteur inferieure ,et refroidies dans leur partie supérieure de la cavité. Nous étudions deux cavités inclinées correspondant à un angle α = 0 et α = 45 degrés .L'écoulement est laminaire et bidimensionnel .Les équations de transfert adimensionnelles exprimées en terme de vorticite et de fonction de courant, ont été résolues avec la méthode implicite des directions alternées à laquelle on a associè la méthode de l'élimination de GAUSS.Nous analysons les effets du nombre de Rayleigh et de l'inclinaison sur les routes vers le chaos qu'emprunte le système.