Max C. Walker, Neil D. Sandham
DOI Number: N/A
Conference number: HiSST-2025-107
Direct numerical simulations (DNS) of a three-dimensional bump on a flat plate are carried out to analyse stability and aero-optic effects in a hypersonic flow field. Bumps are a canonical configuration for shock-wave boundary-layer interactions (SWBLI), which generate a system of shock waves and expansion fans due to geometrical influence. Adverse pressure gradients cause boundary layer separation on both sides of the bump, sustaining instabilities and potentially leading to transition. In compressible flow, aero-optical effects arise from light traversing density fluctuations, where different parts of a wavefront experience varying refractive indices, resulting in image distortion at the aperture. Optical windows require thermal protection due to extreme heating, and cooling methods such as film injection and suction vents are commonly employed. This study compares several blowing and suction configurations, evaluating their impact on both heat flux and optical distortion. The Mach 4 inflow condition corresponds to Mach 6 flight at 28 km altitude, and the DNS captures fine-scale turbulence and shock interactions. The optical path difference (OPD) calculations are validated against the Notre Dame semi-empirical model, showing agreement in attached boundary layers. Results demonstrate that suction schemes reduce downstream heat flux by up to 20% and improve optical performance, while blowing introduces mixing-layer turbulence that can degrade image quality. The study provides insight into the trade-offs between thermal protection and optical clarity, offering guidance for flow control strategies in hypersonic sensor design.