Investigation on Instability of Rayleigh-Benard Convection Using Lattice Boltzmann Method with a Modified Boundary Condition
Publish Year: 1397
نوع سند: مقاله ژورنالی
زبان: English
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شناسه ملی سند علمی:
JR_JCAM-49-2_002
تاریخ نمایه سازی: 18 تیر 1398
Abstract:
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.
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Authors
Mostafa Varmazyar
Department of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran
Mohammadreza habibi
Research Institute of Petroleum Industry, Tehran, Iran
Arash Mohammadi
Department of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran
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