An experimental study of sound generated by flows around cylinders of different cross-section

The sound radiated by rigid cylinders placed transversely in a uniform stream has been measured in an anechoic wind tunnel over a range of Mach numbers ( M = 0.09 – 0.2 ). The cylinders have different cross-sections, e.g., circular, square, rectangular, elliptic, and circular with lateral ribs or knurled surfaces. Different length to diameter ratios of the cylinders are also investigated. Results are presented as narrow band spectra, measured in the far field (acoustic as well as geometric). All spectra are presented with dimensionless (scaled) axes, as well as the original dimensional scales. It is shown that elliptic cross-sections are less noisy, compared to all other cylinders, but noise abatement techniques such as lateral ribs and knurled surfaces can also reduce tonal radiated noise. Two practical applications of these experiments are the reduction of radiated noise from pantographs of high-speed railway trains, and from the landing gear of modern passenger aircraft.