超音速湍流脉动流场气动光学效应分析

Aero-Optic Effects Induced by the Fluctuation Flowfield Surrounding Hypersonic Aircrafts

对高超音速飞行器在大气中飞行时所产生的湍流脉动气动光学效应进行了理论分析与计算.根据CFD计算流场时所使用的湍流模型及其控制方程,推导出流场的折射率脉动方差控制方程.用统计方法,求出该脉动流场的系综平均光学传递函数及相位均方差,从不同角度描述了湍流脉动的气动光学效应.计算结果表明,气动光学传输函数的幅度响应函数具有低通特征,使所获得的图像发生像模糊,而相位响应函数则导致红外成像相位非线性偏移.此外,在相同飞行高度下,马赫数越高,图像模糊越严重.电弧风洞实验结果验证了本文理论分析的正确性.

Computational analysis was carried out regarding the aerooptical effect induced by the turbulence field surrounding the hyperspeed aircraft.The transport equation of the variance of the index of refraction fluctuations was derived based on the scalar transport governing equations of the turbulence model. The refraction fluctuation variances and the fluctuations correlation and phase covariance function along the lineof sight were obtained. Using statistical methods, the turbulent modulation transfer function（MTF） and the refraction correlation function induced in the transmission direction for the refraction fluctuation was computed, which characterized the aerooptical effect in different aspects. Experimental results show that the amplitude response of the transmission function of the aerooptical effect can be characterized as a lowpass filter, which results blurring in the obtained image, while its irregular phase response results nonlinear shifts of the target in the image.And, the higher the Mach number, the more severe the distortion in the image. The correctness of the theoretical MTF was evaluated by wind tunnel experiment.