MULTI-SCALE COHERENT STRUCTURES IN TURBULENT BOUNDARY LAYER DETECTED BY LOCALLY AVERAGED VELOCITY STRUCTURE FUNCTIONS

• Published in: Applied mathematics and mechanics Vol. 26; no. 4; pp. 495 - 504
• Main Author: 刘建华 姜楠 王振东 舒玮
• Format: Journal Article
• Language: English
• Published: Department of Mechanics, Tianjin University, Tianjin 300072, P.R.China 01.04.2005
• Subjects: 一致结构; 局部均匀速度结构函数; 平面因素; 摄动边界层; 流体力学; turbulent boundary layer; coherent structure; intermittency; flatness factor; locally averaged velocity structure function
• ISSN: 0253-4827; 1573-2754
• DOI: 10.1007/BF02465389

The time sequence of longitudinal velocity comtxment at different vertical locations in turbulent boundary layer was finely measured in a wind tunnel. The concept of coarse-grained velocity structure functions, which describes the relative motions of straining and compressing for multi-scale eddy structures in turbulent flows, was put forward based on the theory of locally multi-scale average. Based on the consistency between coarse-grained velocity structure function and Hart wavelet transformation,detecting method was presented,by which the coherent structures and their intermittency was identified by multi-scale flatness factor calculated by locally average structure function. Phase-averaged evolution course for multi-scale coherent eddy structures in wall turbulence were extracted by this conditional sampling to educe scheme. The dynamics course of multi-scale coherent eddy structures and their effects on statistics of turbulent flows were studied.