Ridha Djebali | University of Jendouba Tunisia (original) (raw)
Papers by Ridha Djebali
Cmes-computer Modeling in Engineering & Sciences, 2011
The Lattice Boltzmann method (LBM) became, today, a powerful tool for simulating fluid flows. Its... more The Lattice Boltzmann method (LBM) became, today, a powerful tool for simulating fluid flows. Its improvements for different applications and configurations offers more flexibility and results in several schemes such as in presence of external/internal forcing term. However, we look for the suitable model that gives correct informations, matches the hydrodynamic equations and preserves some features like coding easily, preserving computational cost, stability and accuracy. In the present work, high order incompressible models and equilibrium distribution functions for the advection-diffusion equations are analyzed. Boundary conditions, acceleration, stability and preconditioning with initial fields are underlined which permit to rigorously selecting two LBGK thermal models. The two selected models are modified, leading to two new schemes going well with the above mentioned computational advantages. The standard and modified schemes have been validated on benchmark computations based...
The simplified thermal lattice Boltzmann model (STLBM) developed by Peng, Shu and Chew (2003) is ... more The simplified thermal lattice Boltzmann model (STLBM) developed by Peng, Shu and Chew (2003) is used in this work to simulate low-Rayleigh- number natural convection in a heated rectangular cavity on a uniform grid. It is shown how by resorting to the double populations approach both hydrodynamic and thermal fields can be effectively simulated. Furthermore, a general benchmark is carried out to account for the effect of different parameters in relatively wide ranges. Results are compared with previous works available in the literature.
DESCRIPTION Congrès Français de Thermique 2013 : Thermique & contexte incertain
Applied Mathematical Modelling, 2015
In the present work, two-dimensional mixed convection fluid flow and heat transfer of water-(Cu, ... more In the present work, two-dimensional mixed convection fluid flow and heat transfer of water-(Cu, Ag, Al 2 O 3 and TiO 2) nanofluids in a two-sided facing lid-driven cavity partially heated from below have been investigated numerically. Two discrete heat sources are located on the bottom wall of the enclosure; however, the vertical moving walls and the ceiling are cooled at constant temperature. The remaining boundary parts of the bottom wall are kept insulated. The flow is driven
Communications in Computational Physics, 2013
Revue européenne de mécanique numérique, 2009
Comptes Rendus Mécanique, 2010
Aptitude d'une méthode de type gaz sur réseau pour les écoulements à brisure de symétrie
Ces travaux de these portent sur l'etude du procede de projection par plasma d'arc souffl... more Ces travaux de these portent sur l'etude du procede de projection par plasma d'arc souffle par l'approche Boltzmann sur reseau, LBM. Un modele LBM axisymetrique turbulent a ete developpe, et a servi a la simulation d'un jet de plasma d'argon pure et d'un melange d'argon-azote. Les resultats qui en decoulent sont en excellent accord avec les resultats experimentaux et numeriques de references. Une formulation Lagrangienne a ete adoptee pour l'etude du phenomene de transport de particules eu projection et des transferts plasma-particules durant leurs sejours dans le gaz chaud. La validation, basee sur les histoires dynamique et thermique de particules de zircone ZrO2 et d'alumine Al2O3, a prouve une tres bonne performance de notre modele par comparaison au code "Jets&Poudres". L'accent a ete ensuite nus sur l'effet de la dispersion a l'injection de poudre d'alumine sur le comportement dynamique et thermique de particules eu vol. Nous avons conclu que l'interaction entre ces parametres resulte en un champ de projection plus realiste et que les parametres d'arrivee (a l’impact sur le substrat) sont raisonnables. Nous concluons sur l'efficacite et l'efficience de la methode LBM de rendre bien compte de la physique des milieux multiphases et multiconstituants sous conditions extremes, dont fait partir la projection thermique.
Méthode de Boltzmann pour les écoulements et les transferts: Concept, implémentation et applicati... more Méthode de Boltzmann pour les écoulements et les transferts: Concept, implémentation et applications aux écoulements dans les enceintes et aux jets plasma turbulents PDF TÉLÉCHARGER Méthode de Boltzmann pour les écoulements et les transferts: Concept, implémentation et applications aux écoulements dans les enceintes et aux jets plasma turbulents PDF TÉLÉCHARGER Description
Energy and Built Environment
The study is focused on the use of nanofluids in a micro-open tall cavity, which is a type of mic... more The study is focused on the use of nanofluids in a micro-open tall cavity, which is a type of micro heat exchanger (MHE). The cavity is heated from the bottom sidewall in a sinusoidal pattern, and the effects of four input parameters (Ra, Ha, Kn, and Vf) on heat transfer and irreversibility are investigated using numerical simulations based on Lattice Boltzmann Method (LBM). The findings of the study suggest that the local heat transfer on the bottom sidewall is strongly influenced by Ra and Ha, while the surface distribution of entropy generation is mainly dependent on Kn. The study also shows that the optimization of the magnitude and wavelength of the sinusoidal temperature can improve both local heat transfer and surface distribution of entropy generation. The results of the study provide valuable insights into the design of micro heat exchangers and suggest that the optimization of micro-porous geometries using DOE could lead to increased energy efficiency. The study contributes to our understanding of the complex interactions between input parameters in micro heat exchangers and highlights the importance of considering multiple parameters in the design process.
Acta Mechanica et Automatica
The present study explores magnetic nanoliquid mixed convection in a double lid–driven U-shaped e... more The present study explores magnetic nanoliquid mixed convection in a double lid–driven U-shaped enclosure with discrete heating using the lattice Boltzmann method (LBM) numerical method. The nanoliquid thermal conductivity and viscosity are calculated using the Maxwell and Brinkman models respectively. Nanoliquid magnetohydrodynamics (MHD) and mixed convection are analyzed and entropy generation minimisation has been studied. The presented results for isotherms, stream isolines and entropy generation describe the interaction between the various physical phenomena inherent to the problem including the buoyancy, magnetic and shear forces. The operating parameters’ ranges are: Reynolds number (Re: 1–100), Hartman number (Ha: 0–80), magnetic field inclination (γ: 0°– 90°), nanoparticles volume fraction (ϕ: 0–0.04) and inclination angle (α: 0°– 90°). It was found that the N um and the total entropy generation augment by increasing Re, ϕ: and γ. conversely, an opposite effect was obtained...
2022 13th International Renewable Energy Congress (IREC)
The Lattice Boltzmann (LB) method resolves partial differential equations in LB space and the mor... more The Lattice Boltzmann (LB) method resolves partial differential equations in LB space and the more the number of involved physics and their coupling, the more important the difficulties of conversion to physical space. A general platform conversion between the LB solution space and physical space is provided here. Two test cases on 1D and 2D problems of constant thermophysical properties are presented first and two cases studies of axisymmetric plasma jets of argon and argon-dihydrogen gas were performed for highly variable thermophysical properties on temperature (~20kK) are discussed then. The results of the proposed LB and conversion framework models were found in excellent agreements with experimental and numerical results of classical methods (FDM, FVM) against others LB simulations attempts cited here and presenting substantial deviations.
Article history: Received 26 January 2019 Received in revised form 20 February 2019 Accepted 13 M... more Article history: Received 26 January 2019 Received in revised form 20 February 2019 Accepted 13 March 2019 Available online 22 March 2019 The present study aims to investigate numerically the routes to unsteadiness behavior inside tall cavities at low Prandtl numbers (Pr=0.010.1) under imposed horizontal magnetic field. The transition thresholds are marked under the variation of the cavity aspect ratio Ar=W/H (1/8, 1/4, 1/2), the Rayleigh number Ra (104-5×107) and the Hartmann number Ha (0-150). The Lattice Boltzmann (LBM) approach is used to solve the governing equations. Horizontal temperature gradient is responsible of the convective motion and heat transfer. The changes in the convective flow patterns and temperature contours due to the effects of varying the controlling parameters and associated heat transfer are examined. It has been concluded that the flow is strongly unstable and presents multicellular structure at Pr=0.01 typical of liquid metal compared to Pr=0.1 cases. Th...
Article history: Received 3 December 2018 Received in revised form 23 February 2019 Accepted 28 F... more Article history: Received 3 December 2018 Received in revised form 23 February 2019 Accepted 28 February 2019 Available online 22 March 2019 In this paper a numerical investigation of conjugate natural convection inside a divided square cavity filled with Al2O3-water nanofluid is performed. The lattice Boltzmann method (LBM) is used to solve the governing equations. The nanofluid thermo-physical properties are selected based on literature experimental correlations. The grid independency was checked and the LBM code model was validated on two different cases for wide ranges of the present problem monitoring parameters. A good agreement is obtained by comparison with reported results in the literature. The study of the conjugate heat transfer and nanoliquid motion is, afterward, conducted for the ranges of nanoparticles volume fraction (%): 1 ≤ φ≤ 4, temperature (°C): 20 ≤ T≤ 40, particle size (nm): 15≤ dp≤120 and Rayleigh number: 103 ≤Ra ≤ 106. It will be shown firstly that, at room ...
Cmes-computer Modeling in Engineering & Sciences, 2011
The Lattice Boltzmann method (LBM) became, today, a powerful tool for simulating fluid flows. Its... more The Lattice Boltzmann method (LBM) became, today, a powerful tool for simulating fluid flows. Its improvements for different applications and configurations offers more flexibility and results in several schemes such as in presence of external/internal forcing term. However, we look for the suitable model that gives correct informations, matches the hydrodynamic equations and preserves some features like coding easily, preserving computational cost, stability and accuracy. In the present work, high order incompressible models and equilibrium distribution functions for the advection-diffusion equations are analyzed. Boundary conditions, acceleration, stability and preconditioning with initial fields are underlined which permit to rigorously selecting two LBGK thermal models. The two selected models are modified, leading to two new schemes going well with the above mentioned computational advantages. The standard and modified schemes have been validated on benchmark computations based...
The simplified thermal lattice Boltzmann model (STLBM) developed by Peng, Shu and Chew (2003) is ... more The simplified thermal lattice Boltzmann model (STLBM) developed by Peng, Shu and Chew (2003) is used in this work to simulate low-Rayleigh- number natural convection in a heated rectangular cavity on a uniform grid. It is shown how by resorting to the double populations approach both hydrodynamic and thermal fields can be effectively simulated. Furthermore, a general benchmark is carried out to account for the effect of different parameters in relatively wide ranges. Results are compared with previous works available in the literature.
DESCRIPTION Congrès Français de Thermique 2013 : Thermique & contexte incertain
Applied Mathematical Modelling, 2015
In the present work, two-dimensional mixed convection fluid flow and heat transfer of water-(Cu, ... more In the present work, two-dimensional mixed convection fluid flow and heat transfer of water-(Cu, Ag, Al 2 O 3 and TiO 2) nanofluids in a two-sided facing lid-driven cavity partially heated from below have been investigated numerically. Two discrete heat sources are located on the bottom wall of the enclosure; however, the vertical moving walls and the ceiling are cooled at constant temperature. The remaining boundary parts of the bottom wall are kept insulated. The flow is driven
Communications in Computational Physics, 2013
Revue européenne de mécanique numérique, 2009
Comptes Rendus Mécanique, 2010
Aptitude d'une méthode de type gaz sur réseau pour les écoulements à brisure de symétrie
Ces travaux de these portent sur l'etude du procede de projection par plasma d'arc souffl... more Ces travaux de these portent sur l'etude du procede de projection par plasma d'arc souffle par l'approche Boltzmann sur reseau, LBM. Un modele LBM axisymetrique turbulent a ete developpe, et a servi a la simulation d'un jet de plasma d'argon pure et d'un melange d'argon-azote. Les resultats qui en decoulent sont en excellent accord avec les resultats experimentaux et numeriques de references. Une formulation Lagrangienne a ete adoptee pour l'etude du phenomene de transport de particules eu projection et des transferts plasma-particules durant leurs sejours dans le gaz chaud. La validation, basee sur les histoires dynamique et thermique de particules de zircone ZrO2 et d'alumine Al2O3, a prouve une tres bonne performance de notre modele par comparaison au code "Jets&Poudres". L'accent a ete ensuite nus sur l'effet de la dispersion a l'injection de poudre d'alumine sur le comportement dynamique et thermique de particules eu vol. Nous avons conclu que l'interaction entre ces parametres resulte en un champ de projection plus realiste et que les parametres d'arrivee (a l’impact sur le substrat) sont raisonnables. Nous concluons sur l'efficacite et l'efficience de la methode LBM de rendre bien compte de la physique des milieux multiphases et multiconstituants sous conditions extremes, dont fait partir la projection thermique.
Méthode de Boltzmann pour les écoulements et les transferts: Concept, implémentation et applicati... more Méthode de Boltzmann pour les écoulements et les transferts: Concept, implémentation et applications aux écoulements dans les enceintes et aux jets plasma turbulents PDF TÉLÉCHARGER Méthode de Boltzmann pour les écoulements et les transferts: Concept, implémentation et applications aux écoulements dans les enceintes et aux jets plasma turbulents PDF TÉLÉCHARGER Description
Energy and Built Environment
The study is focused on the use of nanofluids in a micro-open tall cavity, which is a type of mic... more The study is focused on the use of nanofluids in a micro-open tall cavity, which is a type of micro heat exchanger (MHE). The cavity is heated from the bottom sidewall in a sinusoidal pattern, and the effects of four input parameters (Ra, Ha, Kn, and Vf) on heat transfer and irreversibility are investigated using numerical simulations based on Lattice Boltzmann Method (LBM). The findings of the study suggest that the local heat transfer on the bottom sidewall is strongly influenced by Ra and Ha, while the surface distribution of entropy generation is mainly dependent on Kn. The study also shows that the optimization of the magnitude and wavelength of the sinusoidal temperature can improve both local heat transfer and surface distribution of entropy generation. The results of the study provide valuable insights into the design of micro heat exchangers and suggest that the optimization of micro-porous geometries using DOE could lead to increased energy efficiency. The study contributes to our understanding of the complex interactions between input parameters in micro heat exchangers and highlights the importance of considering multiple parameters in the design process.
Acta Mechanica et Automatica
The present study explores magnetic nanoliquid mixed convection in a double lid–driven U-shaped e... more The present study explores magnetic nanoliquid mixed convection in a double lid–driven U-shaped enclosure with discrete heating using the lattice Boltzmann method (LBM) numerical method. The nanoliquid thermal conductivity and viscosity are calculated using the Maxwell and Brinkman models respectively. Nanoliquid magnetohydrodynamics (MHD) and mixed convection are analyzed and entropy generation minimisation has been studied. The presented results for isotherms, stream isolines and entropy generation describe the interaction between the various physical phenomena inherent to the problem including the buoyancy, magnetic and shear forces. The operating parameters’ ranges are: Reynolds number (Re: 1–100), Hartman number (Ha: 0–80), magnetic field inclination (γ: 0°– 90°), nanoparticles volume fraction (ϕ: 0–0.04) and inclination angle (α: 0°– 90°). It was found that the N um and the total entropy generation augment by increasing Re, ϕ: and γ. conversely, an opposite effect was obtained...
2022 13th International Renewable Energy Congress (IREC)
The Lattice Boltzmann (LB) method resolves partial differential equations in LB space and the mor... more The Lattice Boltzmann (LB) method resolves partial differential equations in LB space and the more the number of involved physics and their coupling, the more important the difficulties of conversion to physical space. A general platform conversion between the LB solution space and physical space is provided here. Two test cases on 1D and 2D problems of constant thermophysical properties are presented first and two cases studies of axisymmetric plasma jets of argon and argon-dihydrogen gas were performed for highly variable thermophysical properties on temperature (~20kK) are discussed then. The results of the proposed LB and conversion framework models were found in excellent agreements with experimental and numerical results of classical methods (FDM, FVM) against others LB simulations attempts cited here and presenting substantial deviations.
Article history: Received 26 January 2019 Received in revised form 20 February 2019 Accepted 13 M... more Article history: Received 26 January 2019 Received in revised form 20 February 2019 Accepted 13 March 2019 Available online 22 March 2019 The present study aims to investigate numerically the routes to unsteadiness behavior inside tall cavities at low Prandtl numbers (Pr=0.010.1) under imposed horizontal magnetic field. The transition thresholds are marked under the variation of the cavity aspect ratio Ar=W/H (1/8, 1/4, 1/2), the Rayleigh number Ra (104-5×107) and the Hartmann number Ha (0-150). The Lattice Boltzmann (LBM) approach is used to solve the governing equations. Horizontal temperature gradient is responsible of the convective motion and heat transfer. The changes in the convective flow patterns and temperature contours due to the effects of varying the controlling parameters and associated heat transfer are examined. It has been concluded that the flow is strongly unstable and presents multicellular structure at Pr=0.01 typical of liquid metal compared to Pr=0.1 cases. Th...
Article history: Received 3 December 2018 Received in revised form 23 February 2019 Accepted 28 F... more Article history: Received 3 December 2018 Received in revised form 23 February 2019 Accepted 28 February 2019 Available online 22 March 2019 In this paper a numerical investigation of conjugate natural convection inside a divided square cavity filled with Al2O3-water nanofluid is performed. The lattice Boltzmann method (LBM) is used to solve the governing equations. The nanofluid thermo-physical properties are selected based on literature experimental correlations. The grid independency was checked and the LBM code model was validated on two different cases for wide ranges of the present problem monitoring parameters. A good agreement is obtained by comparison with reported results in the literature. The study of the conjugate heat transfer and nanoliquid motion is, afterward, conducted for the ranges of nanoparticles volume fraction (%): 1 ≤ φ≤ 4, temperature (°C): 20 ≤ T≤ 40, particle size (nm): 15≤ dp≤120 and Rayleigh number: 103 ≤Ra ≤ 106. It will be shown firstly that, at room ...