湍流特征光学测试对比

在10℃～230℃温差下,对大气相干长度r0分别采用夏克-哈特曼的到达角起伏法、差分像运动法、波面法三种测量法和四象限探测器进行了测试和对比;对折射率结构常量Cn2及闪烁功率谱分别采用夏克-哈特曼和光电倍增管进行对比.实验结果表明:对于r0,在强湍流时四象限探测器比夏克-哈特曼的稳定性明显降低,且对夏克-哈特曼三种方法,差分像运动法可克服设备抖动等问题,但引入了方向上不一致的问题,波面法可有效避免该问题;对于Cn2,夏克-哈特曼比光电倍增管测量更稳定,拟合相关系数高达0.96;对于闪烁功率谱,由于噪音影响,在200℃时夏克-哈特曼比光电倍增管测得的最大频率高15Hz;最后,通过对夏克-哈特曼子孔径的闪烁功率谱分析得出,若同一子孔径入射光强不在CCD响应的线性区间时无法准确测量闪烁功率谱,否则可通过不同子孔径可完成湍流均匀性的测量.这将为湍流池提供最优的测试方法及理论依据.

Turbulence Characteristics Optical Test Contrast

During the temperature difference of 10℃~230℃, three kinds of Shack Hartman measuring methods are used to contrast atmospheric coherence length r0 with quadrant detector(QD), and Shack Hartman(SH) and photomultiplier tube(PMT) respectively are applied to contrast refractive index structure parameter C2n with scintillation power spectrum. The experimental results show that: for r0 , the stability of QD decreases more obviously than SH when there is strong turbulence, and for three Shack Hartman methods, DIMM overcomes problems such as device jitter but brings in problem of inconsistency in direction which wave front method can avoid; for C2n, SH is more precise than PMT which fitting correlation coefficient is up to 0.96; for scintillation power spectrum, the maximum frequency SH tested is 15 Hz higher than that of PMT when it is 200℃ influenced by noise; through the analysis of Shack Hartman sub aperture scintillation power spectrum, the scintillation power spectrum is not able to be measured precisely and different sub apertures accomplish the measurement turbulence uniformity when the same sub aperture incident intensity is not in the CCD response linear interval. The results will provide an optimal test method and theoretical basis for turbulence cell.