稳定热分层湍流特性的数值研究

Numerical Study on Turbulent Characteristics of Thermally-Stratified Stable Flow

本文采用大涡模拟方法研究了稳定热分层流动的湍流特性,主要对其中的标量场、速度和温度的脉动量,以及浮力尺度和翻转尺度进行了分析研究.研究结果表明:浮力尺度沿流向随着分层的加强而减小;湍流尺度沿流向先增大然后趋于某个稳定值;在标量场中有高梯度区域产生,且分层抑制这种高梯度区域的产生;温度脉动均方根沿流向先增大然后趋于某个稳定的值,且随着分层的加强,温度脉动均方根沿流向在增大;并且在分层流动中湍流结构呈现出强的各项异性性.

In this paper, the turbulent characteristics of thermally - stratified stable flow are numerically studied in terms of large eddy simulation. Special attention is directed to the scalar field, fluctuating velocity, temperature fluctuation, buoyancy scale and turbulent scale. Results show that the buoyancy scale decreases in the flow direction with the strengthening of stratification. The turbulent scale increases in the flow direction to a certain extent and then gets to a constant value. The high temperature gradient region appears in the scalar field. However, the appearance of the region will be suppressed by stratification. The mean square root of the temperature fluctuation increases first, but then gets to a certain constant value, and, the stronger the stratifica- tion, the larger will be the mean square root of the temperature fluctuation in the flow direction. The structure of turbulence turns out to be highly anisotropic in the thermally - stratified stable flow.