Six planar supersonic jets are computed by compressible large-eddy simulations (LES) using low-dissipation schemes. At the exit of a nozzle of height h, they are ideally expanded and have an exit velocity u_e, yielding a Mach number of M_e = 1.28, and a Reynolds number of Re_h = u_eh/v = 5 × 10~4. Four jets impinging on a flat plate at distances L from the nozzle lips ranging from 3.94h up to 9.1h, with an angle θ between the jet direction and the plate of 90 degrees, are first considered. Two other jets with L = 5.5h and θ = 60 and θ = 75 degrees are also examined. In this way, the effects of both the nozzle-to-plate distance and the angle of impact on the flow and acoustic fields of the jet are studied. Mean velocity flows and snapshots of density, pressure and vorticity are shown. The pressure fields are also described by computing sound pressure levels and using Fourier decomposition. Several tones are obtained in certain cases and their corresponding Strouhal numbers and symmetric or antisymmetric natures are in agreement with experimental data and theoretical models. They are due to an aeroacoustic feedback mechanism occurring between the nozzle lips and the flat plate. This mechanism generates an hydrodynamic-acoustic standing wave revealed by using Fourier decomposition.
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