Unsteadiness of hypersonic flows over a double wedge

Mach 7.10 laminar hypersonic flows with unit Reynolds numbers of 5.2 × 104, 1.04 × 105, and 4.14 × 105 m−1 over a 30/55-deg double-wedge configuration were studied to investigate the spatial-temporal characteristics of the flow in a time-accurate manner. Close comparisons between previous direct simulation Monte Carlo and current Navier-Stokes methods are made to test the validity of the continuum assumption, especially with the existence of large gradients associated with the presence of shock-shock and shock-boundary layer interactions and instabilities. Previous direct simulation Monte Carlo results, which inherently predict rarefied effects such as velocity slip and temperature jumps, are found to be in close agreement with the current work. The impact of velocity slip and temperature jumps on the flow and surface parameters is investigated, and comparisons are made with a no-slip and constant temperature wall model. The temporal variation of three-dimensional flows is thoroughly investigated using two-dimensional and three-dimensional periodic side wall boundary conditions. The existence of spanwise instabilities, even at a relatively low free stream pressure of about 100 Pa, establishesthat the flowfield is dependent on spanwise effects and is three-dimensional.