湍流池湍流特征研究

ON TURBULENT PROPERTY OF CONVECTIVE FLOWS IN A TURBULENT CELL

在用于激光束传输和控制模拟实验的湍流池中温度脉动测量结果表明，原始温度变化曲线上有明显的斜坡（ｒａｍｐ）结构．温度三阶及五阶结构函数和理论预计一致，和大气对流边界层的测量结果相似．斜坡结构的出现对二阶结构函数的影响较小，加热面和冷却面附近有明显的猝发现象出现，温度脉动的峰度系数大于３，表现了较大的间歇性。

The large-scale coherent structures with non-zero odd-order structure function can't be described by Kolmogorov' assumption of local isotropy. Temperature ramps noticed by many researchers are one type of the large-scale coherent structures in the convective boundary layer, obviously exhibit discontinuous ramp face, and can retain their organized characteristic forms for a long time. Temperature ramp may exert a significant effect on the propagation of optical and electromagnetic radiation through the atmosphere. The properties of turbulence, especially ramp structures in a turbulent cell used for simulation of laser propagation and control is carefully analyzed. Based on the data of temperature fluctuation in the turbulent convection cell, the ramp structure can be identified obviously. Three-order and five-order structure function is accordant with the theory, and similar to the results in convective atmosphere boundary layer. Calculation shows that ramp has little effect on the second-order structure function. Close to the heating and cooling surface, there are many distinct bursts, the peak coefficient is lager than 3, the positive skewness of temperature. close to heating face is similar to the convective atmosphere boundary layer. These circumstances show that the flow in ABL is highly intermittent.