Analysis of Boundary-Layer Instabilities in Hypersonic, Three-Dimensional Flows
Abstract
Spatial BiGlobal (SBG) theory was used to study boundary-layer transition on a hypersonic finned cone. A new solver, BLAST, has been developed to apply the equations in a nonorthogonal manner, which extends its applicability to realistic flight vehicles. After verification of the code with previous literature, it was applied to the finned cone at conditions corresponding to quiet wind-tunnel experiments. Boundary-layer instabilities in a horseshoe vortex emanating from the fin-cone intersection are the focus of this study.
Through this investigation, opportunities for improvement were identified regarding SBG and its interpretation. Specifically, the definition of the N factor was used to account for general-group velocity directions. The nonorthogonal equations were used to decouple the orientation of the stability grid from the direction of minimum basic-state change, which allows more control over the most important assumption inherent in spatial BiGlobal. This formulation also allowed computation of the first SBG results to fully include a geometric feature like a full fin in its domain, which is found to be necessary to achieve accurate solutions. The effects of other choices were examined as well, such as the inclusion of streamwise curvature, placement of the azimuthal boundaries, and choice of growth direction. Best practices are developed and discussed.
SBG results are compared with experiments where possible, with particularly good agreement found for a laminar experimental condition at Mach 6 and Re′ = 5.9 × 10^6 m^-1. The correct frequencies are predicted as most-amplified in different regions of the vortex, with the hand-off from one dominant frequency to the other also correctly reproduced computationally. Features of these instabilities are identified, along with their characteristics and how they are affected by the basic state.
Citation
Riha, Andrew Kelly (2022). Analysis of Boundary-Layer Instabilities in Hypersonic, Three-Dimensional Flows. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198502.