Computations of Nonlinear Propagation of Sound Emitted from High Speed Mixing Layers

摘要

Non-linear sound propagation is investigated computationally by simulatingcompressible time-developing mixing layers using the Large Eddy Simulation(LES) approach and solving the viscous Burgers Equation. The mixing layers areof convective Mach numbers of 0.4, 0.8 and 1.2. The LES results agreequalitatively with known flow behavior. Mach waves are observed in the nearsound field of the supersonic mixing layer computed by the LES. These wavesshow steepening typical to non-linear propagation. Further calculations usingthe Burgers equation support this finding, where the initial wave slope has arole in kicking them. No visible non-linear propagation effects were found forthe subsonic mixing layers. The effects of geometrical spreading and viscosityare also considered.