Abstract:
The noise problem caused by pulse exists in the aviation and natural industry, studying sound generation mechanism of the unstable wave is of important significance for understanding, predicting and controlling the aerodynamic noise. In this paper, Nonlinear Disturbance Equation (NLDE) is used to study the relationship between near field dynamic characteristic and the far field sound radiation for supersonic mixing layer. For different types of convective Mach number, disturbance pressure are selected and calculated respectively. It is gained two different sound generation mechanisms. When the convective Mach number of supersonic mixing layer is less than 1, the sound is generated by the large-scale vortex structure in near-field. Otherwise, the generation of sound is depended on whether the phase velocity of disturbance is supersonic relative to the upper flow or not. It turned out that the supersonic part of the disturbance pressure radiate to far-field at a fix angle, that is so called Mach wave radiation. The calculated angle of Mach wave is consistent with the theoretical one.