Analysing the structure of the optical path length of a supersonic mixing layer by using wavelet methods  

作　　者：高穹 易仕和 姜宗福 赵玉新 谢文科 

机构地区：[1]College of Photon-Electron Science and Engineering,National University of Defense Technology [2]College of Aerospace and Material Engineering,National University of Defense Technology

出　　处：《Chinese Physics B》2012年第6期344-351,共8页中国物理B（英文版）

基　　金：Projected supported by the Innovation Research Foundations for Postgraduates of National University of Defense Technology and Hunan Province;the National Natural Science Foundation of China (Grant No. 61008037)

摘　　要：The nano-particle-based planar laser scattering （NPLS） technique is used to measure the density distribution in the supersonic mixing layer of the convective Mach number 0.12, and the optical path difference （OPL）, which is quite crucial for the study of aero-optics, is obtained by post processing. Based on the high spatiotemporal resolutions of the NPLS, the structure of the OPL is ana]ysed using wavelet methods. The coherent structures of the OPL are extracted using three methods, including the methods of thresholding the coefficients of the orthogonal wavelet transform and the wavelet packet transform, and preserving a number of wavelet packet coefficients with the largest amplitudes determined by the entropy dimension. Their performances are compared, and the method using the wavelet packet is the best. Based on the viewpoint of multifractals, we study the OPL by the wavelet transform maxima method （WTMM）, and the result indicates that its scaling behaviour is evident.The nano-particle-based planar laser scattering （NPLS） technique is used to measure the density distribution in the supersonic mixing layer of the convective Mach number 0.12, and the optical path difference （OPL）, which is quite crucial for the study of aero-optics, is obtained by post processing. Based on the high spatiotemporal resolutions of the NPLS, the structure of the OPL is ana]ysed using wavelet methods. The coherent structures of the OPL are extracted using three methods, including the methods of thresholding the coefficients of the orthogonal wavelet transform and the wavelet packet transform, and preserving a number of wavelet packet coefficients with the largest amplitudes determined by the entropy dimension. Their performances are compared, and the method using the wavelet packet is the best. Based on the viewpoint of multifractals, we study the OPL by the wavelet transform maxima method （WTMM）, and the result indicates that its scaling behaviour is evident.

关 键 词：optical path difference AERO-OPTICS supersonic mixing layer WAVELET coherent struc-tures scaling behavior 

分 类 号：O439[机械工程—光学工程]