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Correlating Surface Heat Transfer Rates and Off-Body Spectral Measurements in Roughness Dominated Hypersonic Boundary Layer Transition

AIAA 2024-0938
Session: Instability and Transition II
Published Online:

Boundary layer transition on a 3D-printed ogive with an assortment of nose-tips of varying roughness was studied in Mach 6 conditions with freestream per length Reynolds numbers between 2-8 million per meter. Linear Array-Focused laser differential interferometry (LA-FLDI) was used to measure density fluctuations in the model boundary layer providing off-body power spectral density results and turbulent amplitude information. Simultaneously infrared (IR) imaging was used to measure the surface heat transfer rates. Analysis of wave packet amplitudes determined from bandpassing the LA-FLDI boundary layer measurements show a correlation with the surface heat transfer measurement with respect to changing freestream Reynolds number. Furthermore, the wave packet amplitude analysis provides a quantitative method of identifying transition to turbulent flow with trends supporting the relationship between local heat transfer rates and the intensity of turbulent structures. This trend is also compared to a classical intermittency calculation often used in transitional boundary layer analysis.