Large Eddy Simulationによる音源分布の解析

概要

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Sound source analysis is numerically carried out for aerodynamic sound generated by uniform flow over a square cylinder at a Reynolds number of 10^4. The incompressible time-dependent turbulent flow is first calculated by means of Large Eddy Simulation and the sound generation at the far field is then obtained by surface integral on the square cylinder using the Curle equation modified for low Mach number flows. The sound source intensity distributions on the square cylinder, including negative sound source intensity regions, are shown for three observation points. The time-averaged and instantaneous sound source intensity maps can be used to detect dominant noise origin and to consider the relationship between flow and sound generation. It is demonstrated that estimation of the sound source by observing the large-scale structure of flow is difficult. This is because sound is generated by small timewise fluctuation of the flow. Approximate predictions for the sound source and sound directivity based on timewise fluctuations of the drag and lift are also shown.
1993-11-25