Research of interfacial-refraction-index-thickness approach for simulating large-scale aero-optical distortions

The optical wavefront becomes aberrated when the object optical wavefront propagates through index-of-refractionvariant, turbulent fluid. This paper related optical wavefront distortions to the fluid-mechanical behaviors. It deduces Interfacial-Refraction-Index-Thickness (IRIT) approach on the basis of eikonal equation. It simulated turbulent refractive index field by using high refractive index gradient interfaces instead of the full turbulent information. This simulation method characterized the turbulent flow optical behaviors by refractive index field, introduced the the interfacial physical thickness as the inverse of the refractive index gradient magnitude, and quantified the optical wavefront distortions by the optical path difference (OPD). When compared modeled OPD profile to original full OPD profile, good agreement was found between the original full aero-optical wavefront OPD and the modeled OPD which only retains approximately 50% refractive index information. The results show that large-scale aero-optical distortions emerge from high-gradient interfaces and the IRIT approach is useful to simulate aero-optical effects. Furthermore, it indicates that the IRIT approach can reproduced the large-scale optical distortions using the high-gradient information, and that the IRIT approach can be used for prediction and correction of aero-optical distortions. The IRIT approach can also be used for aero-optical control and optimization by modifying the high-gradient interfaces.