G0500-2-2 Numerical Analysis of Discrete Frequency Noise Generated by Jet from Slit

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  • G0500-2-2 スリット噴流から発生する離散周波数騒音の数値解析([G0500-2]流体工学部門一般講演(2))

Abstract

A subsonic air jet flow from a slit between a flat plate which is parallel to the flow and a wedge which is normal to the flow emits a discrete-frequency aerodynamic noise. In this study, the mechanism of the noise generation is clarified by numerical simulations, and a way to reduce the noise was suggested by results of the simulation. In the simulation, Navier-Stokes equations are directly solved with relatively low order of accuracy, which can be applied to practical designs and improvements of industrial products. The computational results show that the jet flow from the slit emits a discrete-frequency noise and the frequency is close to that of the experimental measurement. The mechanism of the noise generation is clarified by filtering the computational flow field at the frequency, which is the periodical interaction between a vortex generated by the shear layer from the edge of the wedge and that from the edge of the plate. Furthermore, it is shown in the experimental measurement that the discrete-frequency noise is reduced by making the edge of the plate rounded. These results suggest the validity of the computational results and the noise generation mechanism clarified by consideration based on the results.

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