Mach number effect on the aerothermodynamics of transonic and supersonic cavity flows; a computational approach using IDDES

Transonic/supersonic cavity flows exhibit complex fluid dynamics phenomena, such as oscillating shear-layers, flow recirculation, boundary-layer separation, shock/shock and shock/boundary-layer interactions. Computing and characterizing these unsteady flow features have been challenging tasks both experimentally and computationally. The computational prediction of these complex flow phenomena is associated with high-computational cost and thus, computational methods such as large-eddy simulation (LES) and direct numerical simulation (DNS) approaches are not suitable. Therefore, to overcome the computational limitations posed by the DNS and LES approaches, we propose an improved delayed detached-eddy simulation (IDDES) approach for the numerical computation of transonic/supersonic flows. The study shows that IDDES is a suitable, cost-effective and accurate approach for the numerical computation of high-speed turbulent flows. The analysis of the flow physics reveals that the boundary-layer detachment generates a shear-layer which undergoes significant oscillations due to its interaction with the recirculation region inside the cavity. The oscillating shear-layer spans between the fore and rear walls of cavity, and it impinges on the rear-wall of the cavity causing acoustics waves which propagate toward the fore-wall. The cavity causes a flow deceleration from transonic/supersonic flow regimes to subsonic flow regime, and this ensures the combustion stability and flame stabilization. The study also reveals that there is an increase of pressure, temperature and density, with the increase of Mach number. An increase of flow separation with the Mach number was also observed, while the flow separation through the ejection of the boundary-layer causes a decay of the wall temperature.