Görtler Vortices in Hypersonic Flow on Compression Ramps

Abstract

Direct numerical simulation of Görtler vortices in hypersonic compression ramp flow is performed. Three ramp angles of 15, 20, and 25 deg are considered for a freestream Mach number of 7.7 and a unit Reynolds number of . The results show that a mesh resolution of 151 million points is sufficient to capture the flow details. The validation tests present excellent agreement with theoretical values and experimental data. Görtler vortices show unsteady features for the considered ramp flows. The induced heat flux variation and the vortex structure of Görtler vortices are discussed. Two methods of determining the Görtler number are proposed. The first one gives the variation of the Görtler number near reattachment based on the computational results. Additionally, based on a simplified model, a formula depending only on the flow condition and the geometry of the ramp model is deduced to predict the Görtler number. It is shown that the latter method can quantitatively predict the Görtler number near reattachment, and the predictions are in qualitative agreement with a theoretical stability analysis. In the flowfield, corrugated reattachment resulting from the three-dimensionality of the separation bubble is found. Görtler vortices originating in the shear layer as a result of streamline curvature are enhanced at and after flow reattachment.