Aerodynamic sound from a square cylinder with a downstream wedge

Abstract

The effect of placing a wedge in the wake of a square cylinder (side length D) at a Reynolds number of 22,000 is numerically investigated. In particular, the effect of the wedge on aerodynamic noise is observed along with its effect on the flow field. Wedge base height (h) and its gap distance (G) downstream of the cylinder are systematically varied. Flow simulations are carried out using an unsteady RANS model employing the k–ω SST turbulence model, whereas the calculation of aerodynamic noise radiated from the flow is solved using Curle's equation. A special correction technique is applied to consider spanwise effects on noise production and validation is provided using new aeroacoustic data for a square cylinder in cross-flow. It is found that the flow behavior can be divided into two main regimes (regime I and regime II), with a linking transition regime. For regime I, the generated sound is lower than that of the isolated square cylinder case. The thinnest wedge produced the best sound reduction (11.79 dB) when the wedge is placed at G=2D. For regime II, the calculated sound level is higher than the case of an isolated square cylinder. This is because the sound emitted from both bodies have about the same magnitude and are in phase. For this case, the maximum increase of sound pressure is 6.24 dB, when the medium wedge is at G=2.5D.