Numerical analysis on aero-optical wavefront distortion induced by vortices from the viewpoint of fluid density

Abstract

The mixing layer comprised of different-size vortices is the primary optically-active flow causing aero-optical effects for infrared guided vehicles and thus this paper presents a numerical analysis on aero-optical wavefront distortion induced by vortices from the viewpoint of fluid density to explore generation mechanism of the aero-optical effects. A new parameter called relative density difference (RDD) is proposed to build a bridge between the aero-optical wavefront distortion and fluid density on the beam transmission path. The vortices are generated using a cylinder flow which is simulated by the Nektar++, and the ray tracing method is used to calculated wavefront distortion. Simulation cases such as the vortex with different sizes, variable densities, and moving at a constant speed are performed and the results show that density difference of fluid on the beam transmission path has a much greater influence on wavefront distortion than the beam transmission distance, the distorted wavefront will return to a planar wavefront again if an appropriate density fluctuation is imposed on the beam transmission path, and the method of injecting a gas whose density is equal to that of the fluid at the vortex boundary into an optically-active flow is probably effective for reducing aero-optical wavefront distortion induced by vortices in engineering.