Wavefront distortion due to the shock wave and boundary layer in the supersonic flow over a compression ramp

초록

Optical devices equipped in supersonic flight vehicles are subjected to distortions of optical paths due to aero-optical effects, potentially resulting in the degradation of sensing and imaging performance. In this study, the aero-optical effects of the supersonic flow over a two-dimensional compression ramp are investigated through experimental and numerical methods. The experiment is conducted by measuring the wavefront of the laser beam propagated through the test section of a supersonic wind tunnel using a two-dimensional Shack-Hartmann sensor. The individual contribution of the shock wave and boundary layer to the wavefront distortion is identified by conducting a ray-tracing computation through the density of the flow field obtained from a two-dimensional numerical simulation that solves the Reynolds-averaged Navier-Stokes equations. The numerically-obtained wavefront is compared with the time-averaged wavefront measured using the Shack-Hartmann sensor. The deflection angle of the ray at the center of the laser beam is analyzed to assess the aero-optical effects caused by the shock wave and boundary layer. The individual contribution of the shock wave and boundary layer to the wavefront distortion was analyzed for various incidence angles of the laser beam. For the present experimental setup, as boundary layers at the top and bottom walls have the opposite direction of the density gradient, the resultant laser beam deflections are mostly governed by the density gradient across the shock wave. (C) 2021 Elsevier Masson SAS. All rights reserved.

키워드