Tandem cylinder aeroacoustic sources

Abstract

Tandem cylinders in turbulent flow are found in aircraft landing gear, chimney stacks, power lines, and bridge piers. The aim of this paper is to present detailed unsteady surface pressure measurements for tandem cylinders. These unsteady surface pressures are the major sources of noise in this important fundamental test case. A series of experiments were conducted in the UNSW anechoic wind tunnel to investigate the sound generation and flow distortion from a downstream cylinder interacting with wake from an upstream cylinder. This wake is highly anisotropic, containing large vortex shedding scales as well as energetic broadband components. The experiments were conducted using PIV (Particle Image Velocimetry) to obtain instantaneous flow fields and remote microphones to capture unsteady surface pressure measurements. Microphones were positioned outside the flow to record far-field noise. The cylinder was rotated to obtain surface pressure around the circumference. The acoustic results for the tandem cylinder case were compared with noise generation from a single cylinder in uniform flow. An increase in both surface pressure and far-field noise was observed in the tonal and broadband components. It was concluded that interaction with the wake of the upstream cylinder significantly increased the unsteady surface pressure of the downstream cylinder.