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Flow and Acoustic Fields of Rocket Jets Impinging on a Perforated Plate

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The flow and acoustic fields of jets at a Mach number of 3.1 impinging on a plate at 15D of the jet nozzle exit, where D is the nozzle diameter, have been investigated using highly resolved large-eddy simulations. The plate is perforated with a hole of diameter h=1.33D, 2D, 3D, or 4D. The full-plate and free-jet cases have also been considered. The pressure levels are highest for the non-perforated plate and decrease as the hole diameter increases. Compared with the free jet, they are higher by about 5 dB for the full plate, 4 dB for h=1.33D and 2D, 3 dB for h=3D, and 2 dB for h=4D. In the upstream direction, the broadband shock-associated noise is prevailing for the free jet. For the impinging jets, the main noise component in that direction is produced by the impingement of the jet turbulent structures on the plate. In the downstream direction, for the free jet and down to the plate for the impinging jets, the sound field is dominated by Mach waves. Downstream of the perforated plates, waves are generated by interactions between the jet flow and the plate.