运动涡旋脉冲引起的光学畸变

Optics aberrations aroused by moving vorticity pulse

主要研究了气动噪声对光传输和成像的影响。流场求解采用法福尔平均N-S方程,并分别利用基于MUSCL格式的AUSMPW+分裂和二阶中心格式对流通量和粘性通量进行离散处理;用四步四阶Runge-Kutta格式对方程进行时间推进求解,采用J-B两方程模型并经Sarkar方法进行可压缩修正后用于湍流的数值模拟。采用基于光学传递函数的物理光学方法分析平均流动和湍流对光质的影响。研究表明:涡脉冲在运动过程中会引起光束沿涡脉冲运动方向产生较大的整体偏折,偏折幅度随时间而变,最大偏折幅度可以达到1.7μrad;在与涡脉冲运动的垂直方向,整体偏折基本可以忽略不记。在涡脉冲横穿光束的过程中,平均流动会导致焦平面光强峰值有两次下降,平均流动对光强重新分布的影响比湍流脉动影响更强。涡脉冲在运动过程中,先导致光束能量在与涡脉冲运动垂直的方向上扩散,随后使之在涡脉冲运动方向上向外转移。因能量向外扩散,导致Strehl比在0.9 s时刻降低到0.60左右。

Optics aberrations are studied for the case when the aero-noise pulse is propagating through the optical beam. The flow is governed by the Favre-averaged N-S equations. To split the viscosity flux and the convective flux of the N-S equations, the second-order central scheme and the AUSMPW＋ scheme, based on the third-order MUSCL one, are adopted respectively. With the four-step Runge-Kutta scheme in fourth-order, the code is advanced in time. The J-B turbulence model, with the Sarkar＇s compressive modification, is used for turbulence simulations, Aero-optical effects are analyzed with the physics optics by introducing the mean flow OTF（Optical Transfer Function） and turbulence OTF. The results indicate that the moving vorticity pulse can bring the maximal boresight error up to 1.7μrad, and reduce the Streh1 ratio down to 0.60.