带喷流超声速光学头罩流场气动光学畸变试验研究  

Experimental investigation on aero-optical aberration of the supersonic flow passing through an optical dome with gas injection

作　　者：朱杨柱[1] 易仕和[1] 陈植[1] 葛勇[1] 王小虎[1] 付佳[1] 

机构地区：[1]国防科技大学航天科学与工程学院,长沙410073

出　　处：《物理学报》2013年第8期259-266,共8页Acta Physica Sinica

基　　金：国家重点基础研究发展计划(批准号:2009CB724100);国家自然科学基金(批准号:11172326);国防科学技术大学科研计划(批准号:0100010112001)资助的课题~~

摘　　要：超声速光学头罩在大气层内飞行时,需要在光学窗口表面顺来流方向进行喷流冷却,致使窗口上方流场更为复杂.目标光线穿过窗口上方流场,受到激波、膨胀波、混合层、湍流边界层等流场结构引起的变密度场影响而产生波前畸变,导致成像出现偏移、抖动、模糊等气动光学效应.本文对马赫数3.8来流条件下有无喷流时超声速光学头罩流场引起的气动光学波前畸变进行了试验研究.基于纳米示踪的平面激光散射技术,首先对流场图像进行密度校准获得高时空分辨率密度场,然后采用光线追迹法计算得到波长532nm平面光波垂直于光学窗口穿过流场后的光程差(optical path difference,OPD)分布,并对窗口上方近壁区有无喷流状态的流场结构引起的OPD分布进行了研究.发现无喷流时,流场结构相对较为简单,窗口上方有较长的回流区和层流区,而有喷流时窗口上方出现复杂的剪切层、混合层及湍流边界层,流动很快就转捩为湍流结构,其引起的气动光学畸变要明显高于无喷流状态.无喷流状态相隔5μs的流场引起的光程差均方根值分别为0.0348和0.0356μm,有喷流状态的光程差均方根值分别为0.0462和0.0485μm.During the flight in the atmosphere, the optical window of an optical dome needs to be cooled, and supersonic film cooling is one of the economic ways. After traversing through the complex flow field above the window, the optical wave would be distorted by fluctuations in the density field due to the expansion wave, shockwave, mixing layer, turbulent boundary layer, etc. The aero- optical aberrations induced by the flow field of an optical dome in the presence and in the absence of the gas injection at Mach 3.8 are investigated experimentally. Based on the nano-tracer planar laser scattering （NPLS） technique, the density field with high spatial- temporal resolution is first obtained by the flow image calibration, and then the optical path difference （OPD）fluctuations of the original 532 nm planar wavefront perpendicular to the window are calculated using Ray-tracing theory. Also the OPD fluctuations caused by the near-wall region flow structures are presented. In the absence of the gas injection, the flow structure is relatively simple with a long recirculation and laminar region, while in the presence of the gas injection, there appear more complex structures such as shear layer, mixing layer and turbulent boundary layer and the flow is converted into turbulence quickly. Clearly, the optical aberration in the presence of the gas injection is degraded more. For example, the values of root-mean-square OPD （OPDrms） in the absence of the gas injection are 0.038 μm and 0.0356 μm, and they are 0.0462 μm, and 0.0485 μm in the presence of the gas injection during the interval 5 μs.

关 键 词：超声速 喷流 气动光学 光程差 

分 类 号：O436[机械工程—光学工程] O35[理学—光学]