Experimental investigations and prediction of aerodynamic sound generated from square cylinders

Abstract

Aerodynamic sound generated from cylindrical objects, such as in pantographs of trains, is a prime noise source in high speed vehicles. Our objective is to understand the generation mechanism of the aerodynamic sound from two-dimensional cylinders in order to contribute to the prediction and control of high speed vehicle noise. Aerodynamic sound generated from a square cylinder with various angles of attack is measured in relation to the surface pressure fluctuations on the cylinder. Coherent length and the phase characteristics of the surface pressure fluctuations are measured and the aerodynamic sound level is predicted based on the theory of LighthillCurle. Flow around a square cylinder changes drastically at the angle of attack at around 13°, when the separated flow from the leading edge re-attaches on a side surface, and shows the lowest sound level. Predicted sound pressure level agrees well with the measured value for the most range of angles of attack.