Suppression of flow separation in a scramjet inlet using Görtler vortices

This study addresses the issue of boundary layer separation in the inlet of a scramjet engine by employing a strategy centered on Görtler vortices. Numerical simulations are conducted to explore the separation suppression through the use of these vortices at Mach 8. The inlets comprise two-stage compression ramps and a cowl. The turning angle between two ramps is closely related to the occurrence of Görtler vortices and is set at 10° and 15°, with variations in the cowl position. Our findings indicate that the occurrence of Görtler vortices follows a natural transition, and their intensity is influenced by the position of the cowl. The Görtler number, which characterizes Görtler instability, is determined by evaluating the curvature and momentum thickness, both of which are tied to an unsteady separation bubble. The Görtler vortices are intensified by the downstream cowl. A comparison of the results to the two-dimensional cases without vortices reveals that the separation near the throat entrance is effectively suppressed owing to momentum transport by the Görtler vortices. Consequently, the mass flow rate ratio of the duct to the inflow increases significantly, exceeding 0.9. Therefore, the use of Görtler vortices proves to be a valuable method for suppressing critical separation and ensuring the mass flow rate in the inlet duct.