基于小波包方法的超声速气膜气动光学效应相干结构
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摘要
当高速成像制导导弹在大气中飞行时,其光学窗口承受着严重的气动加热。超声速气膜冷却方法可以有效地隔离外部加热,但是超声速气膜流动会引起光束退化,降低图像质量。为了研究超声速气膜气动光学效应,本文构建了主流马赫数为3.4,设计喷流马赫数为2.5,实际测得喷流马赫数为2.45的超声速气膜实验装置。利用基于纳米粒子的平面激光散射技术获得了高时空分辨率流场图像,并对气膜冷却流动的密度场进行重构,利用光线追迹法获取了对应密度场的光程差。通过将光程差分布和K-H涡对比后发现,光程差的波谷位置对应于涡卷的中心,而光程差的波峰对应于涡卷中心之间的连接部分。但是,随着涡结构的发展破碎,对应关系不再成立。根据超声速气膜NPLS流场图像结果,利用分形原理获取的分形维数结果,将其沿流向划分为三个区域,其对应平坦度分别为3.4,2.9,3.6,验证了区域2更适合进行相干结构提取。
While a high-speed aircraft is flying in the atmosphere,its optical hood is subjected to severe aerodynamic heating.Supersonic film cooling method can effectively isolate external heating,but the flow structures formed by the supersonic film cooling can cause beam degradation and affect the imaging quality.To investigate the aero-optics of supersonic film cooling,an experimental model was adopted in this paper,with its mainstream Mach number 3.4,designed jet Mach number 2.5,and measured jet Mach number 2.45.High-resolution images of flow were acquired by the nano-based planar laser scattering(NPLS)technique,by reconstructing the density field of supersonic film cooling,and then,the optical path difference(OPD)was acquired by the ray-tracing method.Depending on the comparison between the K-H vortex and OPD distribution,the valleys of OPD correspond to the vortex‘rollers' and the peaks to the ‘braids'.However,the corresponding relationship becomes quite irregular for the flow field with developed vortices,and cannot be summarized in this manner.According to the NPLS result of the supersonic film flow field,based on the fractal dimension results obtained by the fractal principle,the flow field is divided into three regions along the direction of flow,and the coherent structures of the corresponding OPD are calculated respectively.The corresponding flatness is 3.4,2.9,and 3.6,which verifies that Zone 2 is more suitable for coherent structure extraction.
While a high-speed aircraft is flying in the atmosphere,its optical hood is subjected to severe aerodynamic heating.Supersonic film cooling method can effectively isolate external heating,but the flow structures formed by the supersonic film cooling can cause beam degradation and affect the imaging quality.To investigate the aero-optics of supersonic film cooling,an experimental model was adopted in this paper,with its mainstream Mach number 3.4,designed jet Mach number 2.5,and measured jet Mach number 2.45.High-resolution images of flow were acquired by the nano-based planar laser scattering(NPLS)technique,by reconstructing the density field of supersonic film cooling,and then,the optical path difference(OPD)was acquired by the ray-tracing method.Depending on the comparison between the K-H vortex and OPD distribution,the valleys of OPD correspond to the vortex‘rollers' and the peaks to the ‘braids'.However,the corresponding relationship becomes quite irregular for the flow field with developed vortices,and cannot be summarized in this manner.According to the NPLS result of the supersonic film flow field,based on the fractal dimension results obtained by the fractal principle,the flow field is divided into three regions along the direction of flow,and the coherent structures of the corresponding OPD are calculated respectively.The corresponding flatness is 3.4,2.9,and 3.6,which verifies that Zone 2 is more suitable for coherent structure extraction.
引文
[1]FU J,YI SH,WANG XH,et al..Experimental study on supersonic film cooling on the surface of a blunt body in hypersonic flow[J].Chinese Physics B,2014,23(10):315-322.
[2]朱杨柱,易仕和,陈值,等.带喷流超声速光学头罩流场气动光学畸变试验研究[J].物理学报,2013,62(8):084219-1-8.ZHU Y ZH,YI SH H,CHEN ZH,et al..Experimental investigation on aero-optical aberration of the supersonic flow passing through an optical dome with gas injection[J].Acta Phys.Sin.,2013,62(8):084219-1-8.(in Chinese)
[3]丁浩林,易仕和,付佳,等.雷诺数对超声速气膜气动光学效应影响的实验研究[J].红外与激光工程,2017,46(2):0211002-1-8.DING H L,YI SH H,FU J,et al..Experimental investigation of influence of Reynolds number on supersonic film aero-optics[J].Infrared and Laser Engineering,2017,46(2):0211002-1-8.(in Chinese)
[4]易司琪,丁浩林,龙志强.超声速气膜冷却时的光学性能优化设计[J].应用光学,2017,38(4):20-25.YI S Q,DING H L,LONG ZH Q.Optimal design of supersonic gaseous film cooling optical performance[J].Journal of Applied Optics,2017,38(4):20-25.(in Chinese)
[5]丁浩林,易仕和,付佳,等.超声速湍流边界层气动光学效应的实验研究[J].红外与激光工程,2016,45(10):1018007-1-7.DING H L,YI SH H,FU J,et al..Experimental investigation of aero-optical effect due to supersonic turbulent boundary layer[J].Infrared and Laser Engineering,2016,45(10):1018007-1-7.(in Chinese)
[6]FARGE M.Wavelet transforms and their applications to turbulence[J].Annual Review of Fluid Mechanics,1992,24:395-457.
[7]FARGE M,KAI S,KEVLAHAN N.Non-Gaussianity and coherent vortex simulation for two-dimensional turbulence using an adaptive orthogonal wavelet basis[J].Physics of Fluids,1999,11(8):2187-2201.
[8]FARGE M,PELLEGRINO G,SCHNEIDER K.Coherent vortex extraction in 3Dturbulent flows using orthogonal wavelets[J].Phys.Rec.Lett.,2001,87(5):054501.
[9]FARGE M,KAI S,PELLEGRINO G,et al..Coherent vortex extraction in three-dimensional homogeneous turbulence:Comparison between CVSwavelet and POD-Fourier decompositions[J].Physics of Fluids,2003,15(10):2886-2896.
[10]DAUBECHIES I.Ten Lectures on Wavelets[M].Philadelphia:Society for industrial and applied mathematics,1992:1-2.
[11]DING H L,YI S H,ZHU Y Z,et al..Experimental investigation on aero-optics of supersonic turbulent boundary layers[J].Applied Optics,2017,56(27):7604-7610.
[12]YI S H,TIAN L F,ZHAO Y X,et al..Aerooptical aberration measuring method based on NPLS and its application[J].Chin.Sci.Bull.,2010,55(31):3545-3549.
[13]TIAN L F,YI S H,ZHAO Y X,et al..Study of density field measurement based on NPLS technique in supersonic flow[J].Sci.Chin.Phys.Mech.Astron,2009,52:1357-1363.
[14]GAO Q,YI S H,JIANG Z F,et al..Hierarchial structure of the optical path length of the supersonic turbulent boundary layer[J].Optics Express,2012,20(20):16494-16503.
[2]朱杨柱,易仕和,陈值,等.带喷流超声速光学头罩流场气动光学畸变试验研究[J].物理学报,2013,62(8):084219-1-8.ZHU Y ZH,YI SH H,CHEN ZH,et al..Experimental investigation on aero-optical aberration of the supersonic flow passing through an optical dome with gas injection[J].Acta Phys.Sin.,2013,62(8):084219-1-8.(in Chinese)
[3]丁浩林,易仕和,付佳,等.雷诺数对超声速气膜气动光学效应影响的实验研究[J].红外与激光工程,2017,46(2):0211002-1-8.DING H L,YI SH H,FU J,et al..Experimental investigation of influence of Reynolds number on supersonic film aero-optics[J].Infrared and Laser Engineering,2017,46(2):0211002-1-8.(in Chinese)
[4]易司琪,丁浩林,龙志强.超声速气膜冷却时的光学性能优化设计[J].应用光学,2017,38(4):20-25.YI S Q,DING H L,LONG ZH Q.Optimal design of supersonic gaseous film cooling optical performance[J].Journal of Applied Optics,2017,38(4):20-25.(in Chinese)
[5]丁浩林,易仕和,付佳,等.超声速湍流边界层气动光学效应的实验研究[J].红外与激光工程,2016,45(10):1018007-1-7.DING H L,YI SH H,FU J,et al..Experimental investigation of aero-optical effect due to supersonic turbulent boundary layer[J].Infrared and Laser Engineering,2016,45(10):1018007-1-7.(in Chinese)
[6]FARGE M.Wavelet transforms and their applications to turbulence[J].Annual Review of Fluid Mechanics,1992,24:395-457.
[7]FARGE M,KAI S,KEVLAHAN N.Non-Gaussianity and coherent vortex simulation for two-dimensional turbulence using an adaptive orthogonal wavelet basis[J].Physics of Fluids,1999,11(8):2187-2201.
[8]FARGE M,PELLEGRINO G,SCHNEIDER K.Coherent vortex extraction in 3Dturbulent flows using orthogonal wavelets[J].Phys.Rec.Lett.,2001,87(5):054501.
[9]FARGE M,KAI S,PELLEGRINO G,et al..Coherent vortex extraction in three-dimensional homogeneous turbulence:Comparison between CVSwavelet and POD-Fourier decompositions[J].Physics of Fluids,2003,15(10):2886-2896.
[10]DAUBECHIES I.Ten Lectures on Wavelets[M].Philadelphia:Society for industrial and applied mathematics,1992:1-2.
[11]DING H L,YI S H,ZHU Y Z,et al..Experimental investigation on aero-optics of supersonic turbulent boundary layers[J].Applied Optics,2017,56(27):7604-7610.
[12]YI S H,TIAN L F,ZHAO Y X,et al..Aerooptical aberration measuring method based on NPLS and its application[J].Chin.Sci.Bull.,2010,55(31):3545-3549.
[13]TIAN L F,YI S H,ZHAO Y X,et al..Study of density field measurement based on NPLS technique in supersonic flow[J].Sci.Chin.Phys.Mech.Astron,2009,52:1357-1363.
[14]GAO Q,YI S H,JIANG Z F,et al..Hierarchial structure of the optical path length of the supersonic turbulent boundary layer[J].Optics Express,2012,20(20):16494-16503.