剪切湍流大尺度相干结构的模式研究

MODELLING STUDY OF LARGE-SCALE COHERENT STRUCTURES FOR TURBULENT SHEAR

发展了一种计算剪切湍流大尺度相干结构的新模式．该模式的基础是认为大尺度相干结构为湍流场中流体脉动能量增长最快的那部分，且包含大部分的湍流脉动能量．在此基础上。通过对湍流相干能量方程的推演。建立了描述大尺度相干结构的特征控制方程，并应用Ｃｈｅｂｙｓｈｅｖ多项式方法求得湍流相干能量的最大增长率在波数空间的分布，从而获得对应的大尺度相干结构．应用该模式研究了槽流和一自然对流中的大尺度相干结构，得到的近壁区流动结构与实验现象十分接近．

Large-scale coherent turbulent structures are known to be a fundamental feature in turbulent flows. In this study, the maximum energy growth rate concept is adapted to define the large scales leading to the development of a model approach to resolve the coherent structures. The maximum energy growth rate is obtained here through the perturbation method with the Chebyshev polynomial being applied to solve the characteristic equations governing the behaviour of the large scale coherent structures. Application of the model to the channel flow and the buoyancy flow between two heated vertical plates provides satisfactory results and agree well with the POD results.