Study of Cavity Geometry to Improve Optical Quality of Windows in Hypersonic Flow

Abstract

The optical quality of the window-air system of a flight vehicle in hypersonic flow is simulated. The optical distortion of the window-air system is the metric of merit. Within the earth’s atmosphere, vehicles at hypersonic speeds may generate viscous and high-temperature thermal boundary layers. These boundary layers induce a nonuniform displacement of temperature, density, and fluid velocity over the window-sensor system leading to a degradation of optical quality of the system. The heat f lux into the system is simulated for various geometries (length-to-depth ratios). Computer-simulated flow fields and time-development of different measures of optical quality are produced using US3D. Conjugate heat transfer is used for simulation of solid temperature development, with materials Aluminum-6061 for the vehicle solid (frame) and Sapphire (Al₂O₃) for the window. Optimal window-air system configurations are discussed for a Mach 7 vehicle at 20 km.