Simulation of Natural Convection in a Concentric Hexagonal Annulus Using the Lattice Boltzmann Method Combined with the Smoothed Profile Method

Abstract

This research work presents results obtained from the simulation of natural convection inside a concentric hexagonal annulus by using the lattice Boltzmann method (LBM). The fluid flow (pressure and velocity fields) inside the annulus is evaluated by LBM and a finite difference method (FDM) is used to get the temperature filed. The isothermal and no-slip boundary conditions (BC) on the hexagonal edges are treated with a smooth profile method (SPM). At first, for validating the present simulation technique, a standard benchmarking problem of natural convection inside a cold square cavity with a hot circular cylinder is simulated. Later, natural convection simulations inside the hexagonal annulus are carried out for different values of the aspect ratio, AR (ratio of the inner and outer hexagon sizes), and the Rayleigh number, Ra. The simulation results are presented in terms of isotherms (temperature contours), streamlines, temperature, and velocity distributions inside the annulus. The results show that the fluid flow intensity and the size and number of vortex pairs formed inside the annulus strongly depend on AR and Ra values. Based on the concentric isotherms and weak fluid flow intensity at the low Ra, it is observed that the heat transfer inside the annulus is dominated by the conduction mode. However, multiple circulation zones and distorted isotherms are observed at the high Ra due to the strong convective flow. To further access the accuracy and robustness of the present scheme, the present simulation results are compared with the results given by the commercial software, ANSYS-Fluent®. For all combinations of AR and Ra values, the simulation results of streamlines and isotherms patterns, and temperature and velocity distributions inside the annulus are in very good agreement with those of the Fluent software.

Double-diffusive convection of a nanofluid in a porous cavity containing rotating hexagon and circular cylinders: ISPH simulations

“…For controlling fluid flow because of convection in an enclosure, the researchers are using the detached obstacle of varying shapescircular cylinder (Jami et al, 2007;Angeli et al, 2008;Raizah, 2017;Toghraie et al, 2019;Alsabery et al, 2019;Selimefendigil et al, 2019;Selimefendigil and Öztop, 2015;Selimefendigil and Öztop, 2018), square (Ha and Jung, 2000;Alsabery et al, 2020), triangular (Xu et al, 2009;Sheikholeslami et al, 2015), hexagonal (Gangawane and Manikandan, 2017;Alapati, 2020;El Moutaouakil et al, 2017), elliptical (Bararnia et al, 2011;Tayebi et al, 2019;Dogonchi et al, 2020), wavy shape (Hashemi-Tilehnoee et al, 2020), etc.which are needed for industrial applications. Md et al (2009) analyzed the numerical study of combined free and forced convection between a rectangular cavity and a heat-conducting circular cylinder.…”

“…Also, the presence of a rotating heat source and the direction of rotation affected remarkably the fluid flow and heat transfer. Alapati (2020) presented the simulation of natural convection inside a concentric hexagonal annulus by using the lattice Boltzmann method for evaluating the fluid flow (pressure and velocity fields), a finite difference method to get the temperature field and a smooth profile method to compute isothermal and no-slip boundary conditions (BC) on the hexagonal edges. The results showed that multiple circulation zones and distorted isotherms were observed at the high Ra because of the strong convective flow.…”

External Heating of a Circular Annulus Cavity filled with Nano Fluid.

“…Heat convection investigated for a range of Rayleigh number and different volume fractions for nano-fluid [1]. The noncircular geometry of the internal pipe (rather than circular like square, elliptical, triangular, and hexagonal) attracts the attention also and many investigations have been done on different shapes of the internal pipe rather than circular shape [2,3]. In addition, several boundary conditions for annular spaces have been conducted such as partial heated internal duct [4].…”

A rotating superellipse inside a hexagonalshaped cavity suspended by nano-encapsulated phase change materials based on the ISPH method

“…Seyyedi et al (2020) examined the influences of a magnetic field on entropy generation and natural convection of Cu-H 2 O nano-liquid inside a hexagonal cavity. Alapati (2020) used the lattice Boltzmann method to simulate the natural convection in a concentric hexagonal annulus. Hosseinzadeh et al (2021a, 2021b, 2021c) simulated the heat and flow inside an octagon cavity having an elliptical blocked filled with hybrid nanofluid with water–ethylene glycol contains MoS 2 –TiO 2 hybrid nanoparticles by using the FEM.…”