Reduction of propeller-strut interaction noise by porosity

Crawshaw, Luca, Karimian, Amin, Paruchuri, Chaitanya C., Parry, A.B., Palleja-Cabre, Sergi and Arcondoulis, Elias (2024) Reduction of propeller-strut interaction noise by porosity. In 30th AIAA/CEAS Aeroacoustics Conference, 2024. American Institute of Aeronautics and Astronautics.. (doi:10.2514/6.2024-3386).

Abstract

Propeller operation in close proximity to a strut involves interactions from multiple sources, significantly contributing to noise generation. This study aims to reduce this interaction noise by employing a porous strut as a noise mitigation strategy. The paper presents experimental measurements of far-field noise for three types of rods: two solid rods with varying diameters and one porous rod. These rods were installed both upstream and downstream of the propeller flow at various distances. The porous rod proved to be an effective noise mitigation device, demonstrating reductions in Overall Acoustic Power Levels (OAPWL) of up to 3 dB when placed downstream and up to 6dB when placed upstream of the propeller. The study also introduced an analytical framework designed to predict the unsteady lift on propellers due to porous struts situated downstream. The model utilizes the potential function around porous cylinders to derive the upwash velocity induced on the propeller, thereby estimating the unsteady lift on the propellers. This model provides a valuable tool for understanding and quantifying the noise reduction capabilities of porous struts in practical applications, with the analytical predictions showing trends similar to the experimental data. Numerical simulations are also performed as part of the study to evaluate the unsteady lift from the propeller and understand the flow physics causing these lift variations. These simulations revealed that even minor fluctuations in unsteady loading could lead to substantial increases in radiated noise at higher harmonics, emphasizing the importance of precise control in mitigating noise.

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Contributors

Author: Amin Karimian

Author: Sergi Palleja-Cabre

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