Numerical Computation of the Impulsive Sound Generatedby a Projectile Discharging from a Muzzle

摘要

The goal of this paper is to suggest the numerical method for the simulation ofrnimpulsive sound generation and to investigate the acoustic field produced by a projectile dischargingrnfrom a muzzle. For this problem, a direct simulation using the conventional flow computation methodrnis performed to obtain the acoustic source information in near-field. Computed unsteady flow resultsrnare used to obtain the solutions in far-field. Hybrid method using the flow results computed in nearfieldrnboundary region combined with an integral formulation to evaluate the radiated noise in far-fieldrnis suggested. First, a numerical study on wave dynamic procedure occurring in muzzle flows, whichrnare made by a supersonic projectile released from the open end of a tube into ambient air condition, isrnimplemented. From numerical simulation in near-field, such complex phenomena, including blastrnwaves, jet flows, shock waves and their interactions in the muzzle blast, are described. Second, thernEuler equations assuming axi-symmetric flows, which are able to ensure the non-linear effects whilernpropagating outward and to simulate the near/far-field acoustic propagation, are applied for impulsivernsound propagation resulting from complex muzzle blast through the unsteady flow results computedrnabove. This numerical method is efficient and powerful computation tool to extend impulsive soundrnprediction near-field to the very far-field.