Spatio-temporal evolution of three-dimensional hypersonic double-wedge flows

Spatio-temporal characterization of three-dimensional, unsteady double wedge flows remains an open issue in the hypersonics community. Such a geometrical configuration induces complex phenomena involving shock/shock interaction, boundary layer separation, and thermochemical non-equilibrium. This work presents a detailed comparison of three-dimensional hypersonic flows over a 30°–55° double-wedge for a low enthalpy regime (≈ 2 MJ/kg) and a high enthalpy regime (≈ 8 MJ/kg). Relying on previous results from 2D simulations, the low enthalpy case is expected to be periodic, whereas the high enthalpy flow should reach a steady state after the transient phase. On the contrary, the results presented in this paper do not follow these expectations, reporting an unsteady behavior for both cases. In particular, endothermic chemical processes (molecular dissociation) seem not to affect the unsteadiness of the flow in the case of high free stream enthalpy. For the low enthalpy regime, instead, the flow can be considered frozen. Temporal pressure evolution is collected in numerical probes along the z − axis, in order to assess the asymmetry and unsteadiness of the flow field and to apply a dynamic mode decomposition. Thanks to the in-house multi-graphics processing unit solver, the physical time range covered by the simulations is 40 times larger than the experimental one, providing a dense enough set of data for an appropriate modal analysis.