Abstract
A noise modelling approach is proposed for bluff body wakes such as flow over
a cylinder, where the primary noise source comprises large-scale coherent
structures such as the vortex shedding flow feature. This phenomenon leads to
Aeolian tones in the far-field, and is inherent in wake flows across a range of
Reynolds numbers (Re), from low-Re to high-Re turbulent flows. The approach
employs linear global stability analysis on the time-averaged mean flow, with
amplitude calibration through two-point statistics, and far-field noise
calculations from the global mode fluctuations by Curle analogy. The overall
approach is tested for flow over a cylinder at Reynolds numbers Re=150 and
13300. For Re=150 flow, noise directivity calculations from the present
approach agree with direct far-field computations. For Re=13300 flow, the mean
flow is obtained by particle image velocimetry (PIV). The linear global mode
for spanwise-homogeneous-type fluctuations is obtained at the main, lift
fluctuation frequency. Calibration of this global mode involves Time-Resolved
PIV data in the streamwise-spanwise plane, which is Fourier transformed in
frequency-spanwise wavenumber space. The noise calculations for this global
mode are then found to be less than 1 dB off from the microphone measurements.