scholarly journals MRT-LBM simulation of mixed convection in a horizontal channel heated from below by sinusoidal temperature profile

2020 ◽  
Vol 330 ◽  
pp. 01042
Author(s):  
Nassim Mahfoud Sahraoui ◽  
Samir Houat ◽  
Mohamed El Ganaoui
Keyword(s):  
Rayleigh Number ◽  
Mixed Convection ◽  
Temperature Profile ◽  
Numerical Study ◽  
Oscillation Amplitude ◽  
Horizontal Channel ◽  
Multiple Relaxation Time ◽  
Double Population ◽  
Boltzmann Method ◽  
Sinusoidal Temperature

In this work, a numerical study is carried out to investigate the effect of Rayleigh number on mixed convection in a horizontal channel heated from below by sinusoidal temperature profile and cooled from above. The multiple relaxation time double population thermal lattice Boltzmann method (MRT-TLBM) is used. A validation of our code is done by comparing our results with those found in the literature. Particle oscillation amplitude and temperature profile are plotted for Ra = 5 103, while the Reynolds number, the aspect ratio and Prandtl number are fixed at Re = 10, B=10, Pr = 0.667 respectively. The effect of Rayleigh number on the heat transfer is also discussed.

scholarly journals Simulation of Natural Convection in a horizontal channel with heat sources mounted with porous blocks by the lattice Boltzmann method (MRT-LBM)

2020 ◽  
Vol 307 ◽  
pp. 01009
Author(s):  
Kaoutar BOUARNOUNA ◽  
Abdelkader BOUTRA ◽  
Mahdi BENZEMA ◽  
Mohammed El Ganaoui ◽  
Youb Khaled BENKAHLA
Keyword(s):  
Natural Convection ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Numerical Study ◽  
Darcy Number ◽  
Horizontal Channel ◽  
Multiple Relaxation Time ◽  
Porous Blocks ◽  
Transfer Structure ◽  
Boltzmann Method

In this paper, laminar natural convection in a horizontal channel provided with porous blocks periodically distributed on its lower adiabatic surface has been analyzed. This numerical study is based on the multiple-relaxation-time (MRT) Lattice Boltzmann method (LBM). The two-dimensional model D2Q9 is adopted to solve the flow field, while the D2Q5 model is applied to solve the temperature field. The objective of the study is to analyze the effect of the Darcy number (10-1 ≤ Da ≤ 10-6), Rayleigh number (103 ≤ Ra ≤ 107) and the relative porous blocks height (1/8 ≤ D ≤ 1/2). The obtained results show the important effect of these parameters, which cannot be neglected, on both flow and the heat transfer structure, within this kind of channels.

scholarly journals Improved Energy Efficiency of Mixed Convection Heating Process in Eccentric Annulus

2021 ◽  
Vol 13 (8) ◽  
pp. 168781402110391
Author(s):  
Ben Abdelmlek Khaoula ◽  
Ben Nejma Fayçal
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Rayleigh Number ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Rotation Speed ◽  
Numerical Study ◽  
Heating Process ◽  
Eccentric Annulus

This paper deals with a numerical study of mixed convection heat transfer in horizontal eccentric annulus. The inner cylinder is supposed hot and rotating, however the outer one is kept cold and motionless. The numerical problem was solved using COMSOL Multiphysics® which is based on finite element method. The resolution of the partial differential equations was conducted through an implicit scheme with the use of the damped Newton’s method. The present numerical analysis concerns the effect of eccentricity, rotation speed and Rayleigh number on the flow patterns, heat transfer rate, and energy efficiency of the process. It was found that the heat transfer rate increases with the increase of Rayleigh number. In addition, the heat transfer rate drops with the increase of rotation speed. Finally, we have demonstrated that maximum energy efficiency is achieved not only with higher Rayleigh number but also it is maximum with small eccentricity.

scholarly journals Numerical Investigation of Mixed Convection and Entropy Generation in a Wavy-Walled Cavity Filled with Nanofluid and Involving a Rotating Cylinder

Entropy ◽  
2018 ◽  
Vol 20 (9) ◽  
pp. 664 ◽  
Author(s):  
Ammar Alsabery ◽  
Muneer Ismael ◽  
Ali Chamkha ◽  
Ishak Hashim
Keyword(s):  
Heat Exchange ◽  
Rayleigh Number ◽  
Heat Source ◽  
Mixed Convection ◽  
Volume Fraction ◽  
Numerical Study ◽  
Rotational Velocity ◽  
Geometrical Parameters ◽  
Galerkin Finite Element ◽  
Vertical Walls

This numerical study considers the mixed convection and the inherent entropy generated in Al 2 O 3 –water nanofluid filling a cavity containing a rotating conductive cylinder. The vertical walls of the cavity are wavy and are cooled isothermally. The horizontal walls are thermally insulated, except for a heat source segment located at the bottom wall. The dimensionless governing equations subject to the selected boundary conditions are solved numerically using the Galerkin finite-element method. The study is accomplished by inspecting different ranges of the physical and geometrical parameters, namely, the Rayleigh number ( 10 3 ≤ R a ≤ 10 6 ), angular rotational velocity ( 0 ≤ Ω ≤ 750 ), number of undulations ( 0 ≤ N ≤ 4 ), volume fraction of Al 2 O 3 nanoparticles ( 0 ≤ ϕ ≤ 0.04 ), and the length of the heat source ( 0.2 ≤ H ≤ 0.8 ) . The results show that the rotation of the cylinder boosts the rate of heat exchange when the Rayleigh number is less than 5 × 10 5 . The number of undulations affects the average Nusselt number for a still cylinder. The rate of heat exchange increases with the volume fraction of the Al 2 O 3 nanoparticles and the length of the heater segment.

Numerical Analysis on the Effects of Mixed Convection of Particles Removal Flow over Heated Cavity Using Multi-Relaxation Time Thermal Lattice Boltzmann Method

2014 ◽  
Vol 695 ◽  
pp. 487-490
Author(s):  
Nor Azwadi Che Sidik ◽  
Aman Ali Khan
Keyword(s):  
Distribution Function ◽  
Relaxation Time ◽  
Aspect Ratio ◽  
Mixed Convection ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Numerical Study ◽  
Grashof Number ◽  
Boltzmann Method ◽  
Thermal Lattice Boltzmann

This paper provides numerical study of the effects of mixed convection on particles removal from a cavity using multi-relaxation time thermal lattice Boltzmann method (LBM) for compute the flow and isotherm characteristics in the bottom heated cavity located on a floor of horizontal channel. A point force scheme was applied for particles-fluid interactionand double-distribution function (DFF) was coupled with MRT thermal LBM to study the effects of various grashof number (Gr) and Aspect Ratio (AR) on the efficiency of particles removal. The results show that change in Grashof number and Aspect ratio causes a dramatic different in the flow pattern and particles removal efficiency.

Study of mixed convection in closed enclosure with a ceiling fan

2019 ◽  
Vol 86 (2) ◽  
pp. 20902 ◽  
Author(s):  
Lyes Nasseri ◽  
Omar Rahli ◽  
Djamel Eddine Ameziani ◽  
Rachid Bennacer
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rayleigh Number ◽  
Lattice Boltzmann ◽  
Transfer Rate ◽  
Numerical Study ◽  
Square Cavity ◽  
Flow Intensity ◽  
Vertical Walls ◽  
Boltzmann Method

This paper presents a numerical study of heat transfer by convection in a square cavity. The vertical walls of the cavity are differentially heated and the horizontal ones are considered adiabatic. A fan is placed in the middle of the cavity and releases a jet down. Numerical simulation was performed using the lattice Boltzmann method to show the flow patterns and the heat flux depending on the Rayleigh number (thermal convection intensity) and the Reynolds number (fan-driven flow intensity). A parametric study was performed presenting the influence of Reynolds number (20 ≤ Re ≤ 500), Rayleigh number (10 ≤ Ra ≤ 106) and the fan position (0.2 ≤ HF ≤ 0.8). In forced convection mode, the flow structure has been mapped according to the position and the power of the fan. Three structures have emerged: two symmetrical cells, four symmetrical cells and asymmetrical structure. It has been observed that the heat transfer rate increases with the rise of Reynolds number and the reduction of the distance of the fan position from the ceiling. For the latter one, an unfavorable evolution of Nusselt number is observed for Ra > 104.

scholarly journals Double MRT thermal lattice Boltzmann method for simulating natural convection of low Prandtl number fluids

2016 ◽  
Vol 26 (6) ◽  
pp. 1889-1909 ◽  
Author(s):  
Zheng Li ◽  
Mo Yang ◽  
Yuwen Zhang
Keyword(s):  
Relaxation Time ◽  
Steady State ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Prandtl Number ◽  
Lattice Boltzmann ◽  
Oscillation Period ◽  
Content Type ◽  
Multiple Relaxation Time ◽  
Boltzmann Method

Purpose – The purpose of this paper is to test an efficiency algorithm based on lattice Boltzmann method (LBM) and using it to analyze two-dimensional natural convection with low Prandtl number. Design/methodology/approach – Steady state or oscillatory results are obtained using double multiple-relaxation-time thermal LBM. The velocity and temperature fields are solved using D2Q9 and D2Q5 models, respectively. Findings – With different Rayleigh number, the tested natural convection can either achieve to steady state or oscillatory. With fixed Rayleigh number, lower Prandtl number leads to a weaker convection effect, longer oscillation period and higher oscillation amplitude for the cases reaching oscillatory solutions. At fixed Prandtl number, higher Rayleigh number leads to a more notable convection effect and longer oscillation period. Originality/value – Double multiple-relaxation-time thermal LBM is applied to simulate the low Prandtl number (0.001-0.01) fluid natural convection. Rayleigh number and Prandtl number effects are also investigated when the natural convection results oscillate.

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