Xing Boyang, Zhang Bin, Guo Guangming, Li Dongdong, Liu Hong
Appl Opt. 2021 Sep 20;60(27):8231-8238. doi: 10.1364/AO.434798.
Aero-optical effects in the mixing layer have caused significant concern due to the negative influence of high-speed vehicles with infrared imaging guidance systems. Here, we study the influence of different cooling mediums on the aero-optical effects. Four different cooling components are considered: helium (He), nitrogen (), air, and argon (Ar). The large eddy simulation method and ray-tracing method are used, respectively, to simulate the 3D mixing layer and to calculate the optical path difference (OPD). The numerical results show that, as the molecular weight of the cooling mediums increases, the mixing layer transition advances and the 3D effect of the flow field is enhanced. The local minimum OPD values of the wavefront distortion are significantly correlated with the large-scale vortex structure of the mixing layer. The compression effect plays a dominant role in aero-optics before the large-scale structure forms. Once the large-scale vortex structure generates, the aero-optical effect is conducted by the density and compression effect. The cooling medium helium delays the development of the mixing layer and subsequently reduces the aero-optical effects. However, once the large-scale vortex structure forms, the aero-optical effect becomes serious due to the largest density difference between air and He.
混合层中的气动光学效应因其对配备红外成像制导系统的高速飞行器的负面影响而备受关注。在此，我们研究不同冷却介质对气动光学效应的影响。考虑了四种不同的冷却成分：氦气（He）、氮气（）、空气和氩气（Ar）。分别采用大涡模拟方法和光线追踪方法来模拟三维混合层并计算光程差（OPD）。数值结果表明，随着冷却介质分子量的增加，混合层过渡提前，流场的三维效应增强。波前畸变的局部最小OPD值与混合层的大尺度涡结构显著相关。在大尺度结构形成之前，压缩效应在气动光学中起主导作用。一旦大尺度涡结构产生，气动光学效应由密度和压缩效应主导。冷却介质氦气会延迟混合层的发展，进而降低气动光学效应。然而，一旦大尺度涡结构形成，由于空气与氦气之间最大的密度差，气动光学效应会变得严重。
