Statistics of Heat Transfer in Two-Dimensional Turbulent Rayleigh-Bénard Convection at Various Prandtl Number.

Hui Yang,Yikun Wei,Zuchao Zhu,Yuehong Qian,Huashu Dou

doi:10.3390/e20080582

Hui Yang, Yikun Wei + Show 3 more

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https://doi.org/10.3390/e20080582

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Journal: Entropy	Publication Date: Aug 7, 2018
Citations: 8	License type: CC BY 4.0

Affiliation: Zhejiang Sci-Tech University, Soochow University

Abstract

Statistics of heat transfer in two-dimensional (2D) turbulent Rayleigh-Bénard (RB) convection for and are investigated using the lattice Boltzmann method (LBM). Our results reveal that the large scale circulation is gradually broken up into small scale structures plumes with the increase of , the large scale circulation disappears with increasing , and a great deal of smaller thermal plumes vertically rise and fall from the bottom to top walls. It is further indicated that vertical motion of various plumes gradually plays main role with increasing . In addition, our analysis also shows that the thermal dissipation is distributed mainly in the position of high temperature gradient, the thermal dissipation rate already increasingly plays a dominant position in the thermal transport, can have no effect with increase of . The kinematic viscosity dissipation rate and the thermal dissipation rate gradually decrease with increasing . The energy spectrum significantly decreases with the increase of . A scope of linear scaling arises in the second order velocity structure functions, the temperature structure function and mixed structure function(temperature-velocity). The value of linear scaling and the 2nd-order velocity decrease with increasing , which is qualitatively consistent with the theoretical predictions.

Highlights

Thermal convection generally occurs in natural world and industrial field
Our results demonstrate that the variation characteristics of physical mechanism phenomenon about the kinematic viscosity dissipation, thermal dissipation, energy spectra, temperature spectra and the 2nd structure function with increasing Pr at the same Rayleigh number (Ra)
A large number of small-scale thermal plumes vertically rise from the bottom wall to top wall, a large number of small-scale cold plumes vertically fall from the top wall to the bottom wall, and a great deal of small eddies appear at Pr = 106

Summary

Introduction

Thermal convection generally occurs in natural world and industrial field. Hartmann et al.2001 [1] argued that for weather predictions the flow of atmosphere and thermal convection flow are related with smaller length scales and time scales, and is closely greater scales for climate forecast. Marshall et al (1999) [2] have investigated a key enforcing mechanical properties of ocean circulation in the ocean. Cardin and Olson (1994) [3] have studied that the enforced convection arises in the earth outer core. The effect of rotation, the changing phases, complex boundary conditions and nonlinear dynamic can play a main role in many thermal convections.

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