Aeolian Tones Radiated from Flow Over Bluff Bodies

Abstract

Bluff body is a simple but a central shape for many engineering applications. The geometry shape of the bluff body characterises the behaviour of the flow over the bluff body, where a more complex flow structure is found near downstream. Shear layer separation is mainly responsible for the periodic global phenomena, that includes the generation of sound. The magnitude of the aerodynamically generated sound is dominated by the fluctuations of aerodynamics forces, i.e., drag and lift. The study also shows that the sound pressure field is shaped by the aeolian tones that is related strongly to the lift fluctuations of the bluff body. Amplitude and frequency of the fluctuating lift change naturally with the shape of a particular bluff body. Triangular cylinder exhibits the largest sound pressure level (41.9 dB) followed by ellipse and circular shapes. Square cylinder emits the lowest sound pressure level (36.7 dB). This corresponds to the longest downstream vortex formation length at which for a square cylinder the long vortex formation length provides space for more vortex to dissipate.

Numerical Simulation of Noise Radiated from a Blunt Trailing Edge

“…A maximum of 50.1dB is emitted by the blunt trailing edge when measured at 75D from the trailing edge. The sound field is similar to the sound generated from flow over bluff bodies (e.g., square and circular cylinders [13]). Therefore, any sound reduction mechanism applied for bluff body (equation refer [20]) is also possible to be used for the case of blunt trailing edge.…”

“…The free shear layers that originated from the separation points create a von Kármán vortex downstream. This phenomenon is similar for many bluff body cases [12,13] and it is relevant to the study of aeroacoustic sources like landing gear and high lift devices.…”

“…The Mach number chosen for this study is M = 0.2. Readers are referred to our previous studies [10,13,17] for details on the validation study.…”