The use of compressible parabolized stability equations for prediction of jet instabilities and noise

Abstract

jet has been performed by using the parabolized stability equations (PSE) method. The streamwise evolution of jet instabilities is resolved by the PSE method and so is the induced noise radiation. The direct application of the PSE method to the acoustic field is justified by recognizing that the compressible PSE system asymptotes to the classical wave equations where the mean velocity gradient becomes negligible. The PSE solution shows the unique pressure wave pattern that indicates the Mach wave radiation, as seen in experiments. The contour of the root-mean-squared (RMS) values of the computed perturbation pressure field clearly points out the region of the aerodynamic sources of sound and the direction of jet noise emission. The predicted directions of the noise emission induced by the first helical mode (n = 1) at St = 0.2 and 0.4 are found agreeable with experimental measurements. This agreement is interpreted by the fact that the near-field PSE solution for the n = 1 mode at the same frequencies appears to dominate in the jet flow.