Abstract

The supersonic mixing layer formed on the surface of hypersonic/supersonic flight vehicles’ optical windows is the main structure that induces aero-optical effects (AOEs), which may cause severe imaging degradation. Previous research has found that the ramp vortex generator array (RVGA) with a height of 1 mm can suppress the AOE of a $Mc = {0.17}$ supersonic mixing layer. In this paper, three RVGAs with different heights are considered. The nano-tracer-based planar laser scattering technique and ray tracing method are applied to do the aero-optical analysis. The root mean square of the optical path difference (${{\rm OPD}_{{\rm rms}}}$), Strehl ratio (SR), imaging displacement (ID), and angle deviation (AD) are taken as evaluation parameters. It is found that a smaller aperture size (${{A}_{D}}$) corresponds to a better SR in the aperture size range of ${5}\;{\rm mm}\sim{100}\;{\rm mm}$. Then a beam with an incident angle $\alpha = {15}^\circ$ and a 15 mm ${{A}_{D}}$ is used to study the influence of RVGA’s height on suppressing the AOE. When the RVGA is applied, the ${\overline{\rm ID}}$ and ${\overline{\rm AD}}$ (overline means time-averaged results) in different sections of the supersonic mixing layer are significantly normalized, which can simplify the AOE’s correction procedure. The higher the RVGA is, the more the $\overline{\rm OPD_{rms}}$ is reduced and the weaker the AOE is. RVGA1 ($h = {1.2}\;{\rm mm}$) has the best performance in suppression of the AOE because it introduces much more disturbance than RVGA2 ($h = {1.0}\;{\rm mm}$) and RVGA3 ($h = {0.5}\;{\rm mm}$) and achieves better inhibition of the formation and development of the K-H vortices and more reduction of the whole thickness of the supersonic mixing layer.

© 2022 Optica Publishing Group

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