%0 Journal Article
%T Investigation on Instability of Rayleigh-Benard Convection Using Lattice Boltzmann Method with a Modified Boundary Condition
%J Journal of Computational Applied Mechanics
%I University of Tehran
%Z 2423-6713
%A Varmazyar, Mostafa
%A habibi, Mohammadreza
%A Mohammadi, Arash
%D 2018
%\ 12/01/2018
%V 49
%N 2
%P 231-239
%! Investigation on Instability of Rayleigh-Benard Convection Using Lattice Boltzmann Method with a Modified Boundary Condition
%K Rayleigh-Benard Convection
%K instability
%K Lattice Boltzmann method
%K Bennett Methodology
%K Dimensionless Frequency Ratio
%R 10.22059/jcamech.2017.243410.197
%X In this study, the effects of Prandtl number on the primary and secondary instability of the Rayleigh-Benard convection problem has been investigated using the lattice Boltzmann method. Two different cases as Pr=5.8 and 0.7 representing the fluid in liquid and gas conditions are examined. A body forces scheme of the lattice Boltzmann method was presented. Two types of boundary conditions in the presence of body forces are analyzed by the moment method and applied to a Poiseuille flow. Characteristic velocity was set in such a way that the compressibility effects are negligible. The calculations show that the increment of Prandtl number from 0.7 to 5.8 causes to create a secondary instability and onset of the oscillation in the flow field. Results show that at Pr=5.8, when the Rayleigh number is increased, a periodic solution appeared at Ra=48,000. It is observed that the dimensionless frequency ratio for Ra= 105 with Pr=5.8 is around 0.0065. The maximum Nusselt number for Ra = 105 with Pr=5.8 are estimated to be 5.4942.
%U https://jcamech.ut.ac.ir/article_64208_7ff78497dd6ac7e95a6a4fb5e1874771.pdf