Numerical investigation of aerodynamic noise generated by circular cylinders in cross-flow at Reynolds numbers in the upper subcritical and critical regimes

Abstract

A numerical investigation of the aeroacoustic characteristics of the flow past a circular cylinder is presented for Reynolds numbers in the range $2.67\times {10}^4-3.67\times {10}^5$ , which falls within the upper subcritical and critical regimes. This is based on computational fluid dynamics simulations using a delayed detached-eddy simulation model for the aerodynamics of the near-field, which feeds the equivalent source terms into the Ffowcs Williams–Hawkings equation for far-field noise prediction. The accuracy of delayed detached-eddy simulation in predicting unsteady flow quantities is assessed from an engineering viewpoint through comparisons with experimental data. Good agreement is found for both the near-field flow quantities and the far-field noise spectra. The aerodynamic and aeroacoustic characteristics are investigated from two aspects: the effect of varying the Reynolds number and the sensitivity to the spanwise computational dimension. The results in terms of the vortex shedding frequency, hydrodynamic forces and far-field noise levels only show small variations in the subcritical range. However, in the critical range, the vortex shedding frequency increases and the noise level decreases considerably after allowing for the typical sixth power dependence. A spanwise length of 3D is found to be sufficient for most Reynolds numbers in the critical range; but in the subcritical range, a longer spanwise length is needed, and the sound level may be under-predicted by up to around 4.5 dB by using 3D.