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Temporal evolution of the optical path difference of a supersonic turbulent boundary layer

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Chinese Physics B 2013年第1期22卷 231-236页

作者：高穹易仕和姜宗福何霖谢文科 College of Photon-electron Science and Engineering National University of Defense Technology College of aerospace and Material Engineering National University of Defense Technology

The density distribution of a supersonic turbulent boundary layer is measured with the nanoparticle-based planar laser scattering technique, and the temporal evolution of its optical path difference （OPD） in a short time interval is characterized by proper orthogonal decomposition （POD）. Based on the advantage of POD in capturing the energy of a signal, a temporal evolution model is suggested for the POD coefficients of the OPD. In this model, the first few coefficients vary linearly with time, and the others are modeled by Gaussian statistics. As an application, this method is used to compute the shortexposure optical transfer function.

关键词： aero-optics supersonic turbulent boundary layer optical transfer function

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

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Chinese Physics B 2012年第6期21卷 344-351页

作者：高穹易仕和姜宗福赵玉新谢文科 College of Photon-Electron Science and Engineering National University of Defense Technology College of aerospace and Material Engineering National University of Defense Technology

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

Universal form of the power spectrum of the aero-optical aberration caused by the supersonic turbulent boundary layer

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Chinese Physics B 2014年第10期23卷 118-123页

作者：高穹易仕和姜宗福 College of Photon–Electron Science and Engineering National University of Defense Technology College of aerospace Science and Engineering National University of Defense Technology

Based on the measurement of one-dimensional （1D） optical path difference （OPD） of the supersonic turbulent bound- ary layer, an analytical form for the power spectrum of the two-dimensional （2D） OPD is obtained with its structure function and under the locally homogeneous isotropic assumption. The universality of this spectrum is argued, and its validity is checked by the comparison with experimental result. The potential applications of this model in theoretical and numerical studies are emphasized. Another contribution of this work is around the application of correlation function to analyzing the statistics of OPD. Based on our results and other results published elsewhere, we show that the OPD is often not stationary, and one should be cautious about using this tool.

关键词： aero-optics supersonic turbulent boundary layer optical path difference power spectrum

An experimental study of aero-optical aberration and dithering of supersonic mixing layer via BOS

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Science China(Physics,Mechanics & Astronomy) 2010年第1期53卷 81-94页

作者： ZHAO YuXin , YI ShiHe, TIAN LiFeng, HE Lin & CHENG ZhongYu College of aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China College of aerospace and Material Engineering National University of Defense Technology Changsha China

The optical performance of supersonic mixing layer is heavily deteriorated by the aero-optical aberration and dithering of coherent structures, but current measuring methods limit the spatiotemporal resolution in relevant studies. A high resolution whole-field aero-optical aberration and dithering measuring method based on the Background Orient Schlieren (BOS) technique was studied. The systematic structure, sensitivity and resolution of BOS are analyzed in this paper. The aero-optical aberration and dithering of streamwise structures in supersonic mixing layers were quantificationally studied with BOS. The aberration field of spanwise structures revealed the ribbon-like aberration structures, which heavily restrict the optical performance of a mixing layer. The quantifications of aero-optical aberration and dithering are very important in studying aero-optical performance of supersonic mixing layer.

关键词： aero-optics supersonic mixing layer BOS

aero-Optical Characteristics of Supersonic Flow over Blunt Wedge with Cavity Window

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Journal of Shanghai Jiaotong university(Science) 2011年第6期16卷 742-749页

作者：李波刘洪 School of Naval Architecture Ocean and Civil Engineering School of aeronautics and Astronautics Shanghai Jiaotong University

The optical rays that form the image of an object and propagate a supersonic flow over a vehicle are refracted by the density variations.A numerical analysis of the aero-optical characteristics of supersonic flow over blunt wedge with a cavity window is carried out.A hybrid method of Reynold averaged Navier-Stokes and direct simulation Monte Carlo(RANS/DSMC) is employed to simulate the flowfield.Refraction factor is introduced to evaluate the flowfield's aero-optical characteristic.The results show that mean flow's aero-optical effects are mainly caused by the shock wave,the expansion wave and the turbulent boundary layer.Fluctuation flow's aero-optical effects are mainly caused by the turbulent boundary layer and the shock wave induced by the cavity window.The aero-optical effects at the leading side of window are caused by the mean density variations,while the effects at the trailing side are caused by the density fluctuations.Different draft angles of the cavity window are investigated.The airborne optical devices of supersonic vehicle should be mounted in the middle of the cavity window with a large draft angle.

关键词： aero-optics supersonic flow blunted wedge cavity window