关键词: Rayleigh-Bnard热对流/
Prandtl数/
湍流特性/
温度边界层
English Abstract
Numerical study of Prandtl number effects in turbulent thermal convection
Bao Yun,Gao Zhen-Yuan,
Ye Meng-Xiang
1.Department of Mechanics, Sun Yat-Sen University, Guangzhou 510275, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant Nos. 11772362, 11452002), the Special Scientific Research Fund for Super Computing in the Joint Fund of the National Natural Science Foundation of China, and the People's Government of Guangdong Province (PhaseII)(Grant No. nsfc2015_570).Received Date:03 July 2017
Accepted Date:18 October 2017
Published Online:05 January 2018
Abstract:The high-resolution numerical simulations of two-dimensional (2D) turbulent Rayleigh-Bnard convection are conducted by using the Parallel direct method of DNS (PDM-DNS) with Ra=1010 and Pr in a range from 0.05 to 20. Using the flow visualization technique, the effects of Pr on the structure of plumes and large scale circulation (LSC) are investigated. With Pr decreasing, plumes become more active and the flow turns more turbulent. When Pr4.3, pronounced LSC and corner vortex exist. The thickness of thermal boundary layer varies slightly with the value of Pr changing, which obeys a scaling law. Nusselt number (Nu) increases with Pr value increasing when Pr value is low and becomes independent when Pr value is high. Furthermore, two definitions of Reynolds number (Re) are given. The Re?u? angle is calculated from the fluctuation of horizontal velocity near the center of bottom plate, and the ReUmax is calculated from maximal horizontal velocity in the mean field. Both of them follow the same scaling Re~Pr0.81.
Keywords: Rayleigh-Bnard convection/
Prandtl number/
turbulence/
thermal boundary layer
