中国物理B ›› 2012, Vol. 21 ›› Issue (6): 64701-064701.doi: 10.1088/1674-1056/21/6/064701

• ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS • 上一篇    下一篇

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

高穹a, 易仕和b, 姜宗福a, 赵玉新b, 谢文科a   

  1. a. College of Photon-Electron Science and Engineering, National University of Defense Technology, Changsha 410073, China;
    b. College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China
  • 收稿日期:2011-10-17 修回日期:2011-12-06 出版日期:2012-05-01 发布日期:2012-05-01
  • 基金资助:
    Projected supported by the Innovation Research Foundations for Postgraduates of National University of Defense Technology and Hunan Province, and the National Natural Science Foundation of China (Grant No. 61008037).

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

Gao Qiong(高穹)a)†, Yi Shi-He(易仕和)b), Jiang Zong-Fu(姜宗福)a), Zhao Yu-Xin(赵玉新)b), and Xie Wen-Ke(谢文科)a)   

  1. a. College of Photon-Electron Science and Engineering, National University of Defense Technology, Changsha 410073, China;
    b. College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China
  • Received:2011-10-17 Revised:2011-12-06 Online:2012-05-01 Published:2012-05-01
  • Contact: Gao Qiong E-mail:gaoqiong1980@126.com
  • Supported by:
    Projected supported by the Innovation Research Foundations for Postgraduates of National University of Defense Technology and Hunan Province, and 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 analysed 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 structures, scaling behavior

Abstract: 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 analysed 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.

Key words: optical path difference, aero-optics, supersonic mixing layer, wavelet, coherent structures, scaling behavior

中图分类号:  (Supersonic and hypersonic flows)

  • 47.40.Ki
47.80.Jk (Flow visualization and imaging) 47.53.+n (Fractals in fluid dynamics) 42.25.Dd (Wave propagation in random media)