Vamsi Krishna TALLURI, Jacob COHEN, Soumya R. NANDA

DOI Number: N/A

Conference number: HiSST-2025-274

The transition of boundary layers in hypersonic flows plays a decisive role in the design of thermal protection systems and the overall integrity of high-speed vehicles. This study investigates the influence of cylindrical surface roughness on the laminar–turbulent transition within a hypersonic boundary layer. Experiments were conducted in a Ludwieg tube facility using a wedge model fitted with cylindrical roughness elements of varying relative heights, corresponding to height-to-boundary-layer-thickness ratios (h/δ) of 0.46, 0.77, and 1.15. Flow evolution downstream of the roughness was examined through high-speed Schlieren imaging and Planar Laser Rayleigh Scattering (PLRS), while unsteady pressure sensors embedded in the surface provided quantitative measurements of pressure fluctuations. The findings show that larger roughness elements significantly advance the transition location. The tallest trip (h/δ = 1.15) produced substantial boundary layer thickening and the formation of vortical structures characteristic of turbulence. Pressure measurements revealed elevated root-mean-square (RMS) levels due to the transition. Furthermore, Proper Orthogonal Decomposition (POD) of spanwise PLRS data confirmed the emergence of coherent vortical structures downstream of x/D > 3.5 for the higher trip cases.

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In Categories: 1.Events, 1.HiSST 2025, High-Speed Aerodynamics and Aerothermodynamics with application to hypersonic regimes
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