稳定分层湍流中逆梯度输运的关联分析研究

本文采用关联分析方法研究了稳定温度分层湍流中的结构特性、输运特性，以及热量、动量逆梯度输运现象的尺度效应及其参数演化．首先采用大涡模拟方法对稳定分层湍流中的结构特性和输运特性进行了分析，将逆梯度输运发生的时间尺度作为已知条件，结合关联量分析方法在波数空间中的解析解，对逆梯度输运现象的尺度效应进行了分析研究．结果发现，稳定分层强度较大的流动中发生垂向热量及动量逆梯度输运现象，发生的结构尺度与关联分析所发现垂向热量、动量逆梯度输运的波数形成了呼应．随着分层强度增加，热量、动量的输运强度均受抑制，与逆梯度输运关联的流场结构尺度减小，同样的效应也发生在流场结构向下游演化的过程中．

Correlation Analysis on Counter-Gradient Transport in Stably Stratified Turbulence

In this paper, the structure characteristics and transport characteristics, as well as the scale effect and parameter evolution of heat and momentum counter-gradient transport (CGT) in stably temperature stratified turbulence are investigated with correlation analysis method. The large eddy simulation is employed to analyze the characteristics of both structure and transport properties in the stratified turbulence. Regarding the time scale of CGT, which is gained from the simulation, as a known condition, the scale effect of CGT is studied using the analytic solution of correlation equations in the wavenumber space. The results show that the vertical heat and the momentum CGT occur in the stratified turbulence with high intensity of temperature stratification. The structure scale of CGT corresponds with the wavenumber, with which the CGT phenomena is found in correlation analysis. As the stratification intensity increases, the intensity of transport, including CGT, of the thermal flux and the momentum transport are suppressed and the relevant structure scale decreases. The same effect also occurs in the process of the flow structure downstream evolution.