Simulation of the impact of propagation through optical fluids and turbulent flow on optical system performance

Performance and reliability requirements for modern optical systems dictate that they can no longer be simulated in isolation without reference to external and environmental factors which can adversely impact image quality. Simultaneously, advances in multi-physics simulation techniques have made it possible to couple the impacts of, for example, thermal changes and structural stresses to optical analysis to better predict performance in operational conditions. Applications where light propagates through a fluid surrounding or within an optical system present a particular simulation challenge in this regard, and one that requires new simulation techniques. In the near-field, variations in pressure, temperature, and density of the fluid give rise to corresponding variations in refractive index that will, in turn, induce optical aberrations in a transmitted wavefront. These aberrations can lead to degraded image quality and line-of-sight errors. Accurate and robust analysis of such effects necessitates the coupling of computational fluid dynamics (CFD), for simulation of turbulent flow, shock waves, etc. with ray tracing to compute key optical metrics. Furthermore, this analysis can be combined with far-field atmospheric effects, including emissivity, absorption, scattering, refraction, to build a comprehensive picture of system performance. The ability to perform multi-physics simulations early in the design process provides the opportunity to develop strategies to identify and mitigate negative performance drivers. We present a solution to model the effects of light propagation through optical fluids accurately and combine this with analysis of structural and thermal effects. This solution will be demonstrated in use cases including electro-optic infrared airborne systems.