Numerical investigation on aerodynamic noise of flow past a cylinder with different spanwise lengths

Abstract

A numerical investigation is conducted on aerodynamic noise of flow past a circular cylinder with different spanwise lengths (0.5πD, πD, 2πD, 4πD) at Re = 10, 000, where D is the diameter of the cylinder. The near-field pressure and velocity fields are predicted through Large Eddy Simulation (LES), then the acoustic analogy is used to obtain the far-field noise. The results show good agreements for both the near and far-field with the data from in-house experiments and the literature. Though the spanwise length has limited influence on the power spectral density of the near-field velocity and pressure fluctuations at different spanwise locations, substantial differences are observed for the spanwise pressure coherence and near-wake structures. The 0.5πD case shows primarily two-dimensional flow features immediately behind the cylinder compared to the other three cases, resulting in the overprediction of the spanwise pressure coherence, which has strong implications for the far-field noise prediction. With the spanwise length correction, the differences in overall noise magnitudes of the different cases diminish. Nevertheless, the 2πD and 4πD cases better capture the first and second harmonics of the vortex shedding and its associated directivities than the other two cases, showing the importance of sufficient spanwise lengths in predicting noise from flow past a cylinder.