LES of Compressible Impinging Round Jets at varying impinging distances and Mach numbers

Compressible round jets impinging on a flat surface can have engineering applications such as rocket propulsion and Short Take-Off Vertical Landing (STOVL) aircrafts. Such impingement of high-speed jets can result in a complex interplay of shock waves, turbulent shear layers and acoustic feedback loop that results in discrete tonal noise. In the present work, we present results from well-resolved Large Eddy Simulations for three flow cases - two subsonic cases at Mach number 0.9 but varying inlet to plate distances of h=8r₀ and h=4r₀, where r₀ is the jet radius at inflow. The third case is a supersonic case at Mach 1.5 and h=8r_0. The Reynolds number of the jets based on the inlet diameter and centerline velocity is 25000. The LES results are obtained using 6^th order compact central scheme alongwith an explicit filtering approach based on the approximate deconvolution method. An additional adaptive filter is used near the shocks.



The flow fields in all three cases show the presence of weak shocks. As expected, the shocks are significantly stronger in the supersonic case. Between the two subsonic cases, these values are higher in the h=4r₀ case as expected, due to the shorter axial distance. This case also shows only one distinct shock in the flow as opposed to two shocks in the other two cases. Detailed turbulence statistics will also be presented at the conference.