本征正交分解在气动光学畸变仿真中的分析与应用

通过本征正交分解研究湍流流场相干结构和所造成的气动光学畸变间的关系.以高速导弹红外窗口绕流流场的计算流体力学结果为源数据,通过奇异值分解实现流场折射率场的本征正交分解.比较折射率场的低阶奇异值和源数据产生的气动光学畸变参数光程差,二者有很好的吻合性.由此提出一种采用折射率场的奇异值直接仿真光程差的简易算法.仿真表明只利用二维折射率场的第一阶奇异值即能描述畸变波前的特性,其光程差的相对误差不超过±2%,验证了湍流中的相干结构造成了大部分的气动光学畸变.

PROPER ORTHOGONAL DECOMPOSITION APPLIED IN THE ANALYSIS OF SIMULATING AERO-OPTICAL DISTORTIONS

The connection between coherent structure in turbulence and the aero-optical distortions was studied through proper orthogonal decomposition(POD).The computational fluid dynamics(CFD) solutions of high speed turbulence around a missile IR window were used as resource data.Singular vector decomposition was adopted to achieve POD for the spatial-dependent mean flow field.As optical path difference(OPD) is often used to describe optical performance,the low-order singular value of the refractive index fields has good agreement with OPD caused by the source data.Then a plain method for simulating aero-optical distortions was proposed,in which only singular values of refractive index were used.By using the first order singular value,the method can represent the characters of aberrated wave-front,and the relative error of OPD is no more than 2%.The results also validate the argumentation that most aero-optical distortions are caused by coherent structure.