Measurement of Surface Heat Flux Due to Fin-Induced Shock-Boundary Layer Interactions
Abstract
In high-speed flows, fins cause shock-boundary layer and shock-shock interactions that result
in complicated, 3D flow fields, with heating being the primary concern to vehicle designers and
engineers. A methodology has been developed to study fin-induced shock-boundary layer interactions (SBLI) at Texas AM University. Wind tunnel models were 3D printed from Formlabs
Rigid 10K resin using a Formlabs 3L printer. To accurately quantify heating caused by fins, a new
method was developed to convert infrared temperature measurements into heat flux using the full, 3D heat equation. The fin-cone model with a single, highly swept fin on a 7° half-angle cone was printed and tested, replicating the same pressure frequency spectra and heat flux patterns as measured on PEEK and stainless steel models in other wind tunnels and computational simulations. Multi-fin models comprised of interchangeable conical and ogive fore-bodies paired with 3 or 4 fin cylindrical rear-sections were used to generate shock-boundary layer interactions in the Actively Controlled Expansion Tunnel and Mach 6 Quiet Tunnel at Texas A&M University. Experiments on blockage models of the multi-fin geometries were used to lay the groundwork for CFD and stability analysis validation studies. Infrared data mapping to the solution domain was demonstrated to be accurate within the mesh resolution and the solutions were found to be converged for mesh density. Model alignment studies found that the number of and location of vortex structures could be affected by less than 1° of misalignment. Increasing unit Reynolds number supported stronger SBLI, with more secondary vortices and higher heating levels. These effects seemed to dominate any differences due to model geometry. The 3D heat flux tool was found to be limited in that peak heating often occurred at sharp corners, requiring larger meshes than could be supported to fully resolve those geometric features. Additionally, the data processing time for the entire process averaged at least one day per run if started entirely from scratch and processed in series. Overall, the 3D, heat flux reduction tool reduced the discrepancy between old 1D tools and CFD by 50% on the fins and prepare the way for simultaneous infrared and pressure studies of SBLI on multi-fin geometries.
Citation
Wirth, John M (2021). Measurement of Surface Heat Flux Due to Fin-Induced Shock-Boundary Layer Interactions. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /196393.