Aeroacoustic investigation of active base blowing applied to a structured porous cylinder

Maryami, Reza, Arcondoulis, Elias and Liu, Yu (2023) Aeroacoustic investigation of active base blowing applied to a structured porous cylinder. In AIAA Aviation 2023 Forum. (doi:10.2514/6.2023-3742).

Abstract

An experimental study was conducted to investigate the effectiveness of local blowing (LB) to suppress vortex-induced noise of a circular cylinder at ���� = 0.7 × 105. The far-field noise was synchronised with surface pressure fluctuations and velocity field in the wake to understand the underlying mechanism of LB noise reduction. A series of specially designed chambers were used to apply LB in the boundary layer (���� = ±41○) and separated region (���� = ±90○ and ±131○) within ���� = 0.007 − 0.036. It was observed that all LB cases except the LB at ���� = ±90○ are capable to reduce tonal noise from the baseline over the range of ���� yet the application of LB in the boundary layer presented a superior reduction. It was proved that vortex shedding is the primary mechanism for inducing surface pressure fluctuations and propagating sound waves into the far field. While the vortex shedding as a hydrodynamic pressure field is prone to radiate acoustic waves into the far field, the coherence between the near and far field pressure signals confirmed that the pressure fluctuations induced on the cylinder surface specifically in the pre-and post-separation regions are mostly responsible for tonal noise. It was found that the LB at ���� = ±41○ pushes vortex shedding further downstream in comparison to other LB cases and there is a region of low turbulent kinetic energy close to the cylinder, which is consistent with suppressing vertical flow movement and thus surface pressure fluctuations.

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Contributors

Author: Elias Arcondoulis

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