Role of corner flow separation in unsteady dynamics of hypersonic flow over a double wedge geometry

TL;DR

This paper investigates the unsteady shock oscillations in hypersonic flow over a double wedge, revealing how shock interactions near the wedge influence flow unsteadiness through detailed numerical simulations.

Contribution

It provides new insights into the conditions causing self-sustained oscillations in hypersonic double wedge flows, especially regarding shock positioning and wedge geometry effects.

Findings

Unsteady oscillations occur when shock is near the aft wedge expansion corner.

Flow remains steady if the shock is far from the aft wedge corner.

Wedge angle and length ratios significantly influence flow unsteadiness.

Abstract

This study investigates the origin and sustenance of self induced oscillations of shock structures in a hypersonic flow over a double wedge configuration. Previously, various researchers have considered the double wedge flow configuration for inviscid flow with variations of different inflows as well as geometric parameters such as inflow Mach number , wedge angles, and wedge lengths. Few recently published articles reveal an unsteady flow physics involved with the hypersonic viscous flow for double wedge configuration with large second wedge angles. However, the reason for such self sustained flow oscillations is not completely clear. The present work seeks out to investigate the origin of such oscillations in a low enthalpy hypersonic flow with different aft wedge angles and wedge length ratios.In the current study, viscous flow over a double wedge at Mach 7 and fore wedge angle of 30{\deg} is considered. An improved version of rhoCentralFoam solver in OpenFOAM is used to investigate the double wedge flow over different grid resolutions in the separation region and shock shock interaction region. This study corroborates the observation from the previous literature with an improvement in the range of parameters which results in a self sustained periodic oscillation. The present study also suggests that the unsteadiness becomes possible when the incidence shock is in the proximity of the aft wedge expansion corner as a consequence of different wedge length ratios(L1/L2) or aft wedge angles ({\theta}2). Flow can still be steady at a large aft wedge angle if the incidence shock is far ahead of the aft wedge expansion corner.