On the modelling of a porous strut installed below a UAV propeller

quietdrones2026 Tracking Number 2

In small unmanned aerial vehicle (UAV) systems, propellers operating in close proximity to a supporting strut often induce abrupt variations in aerodynamic loading, generating strong impulsive noise. Recent studies have shown that replacing a rigid strut with a porous one can effectively mitigate this interaction noise. This paper proposes a boundary element method (BEM) for predicting the unsteady pressure field around a porous strut located below a propeller. The proposed method models the acoustic propagation within the strut by modelling the porous medium as an equivalent fluid with properties determined using the Delany & Bazley model. This approach avoids the complexity of modelling this problem using a computational fluid dynamics/aeroacoustics (CFD/CAA) technique. The method involves solving two coupled Helmholtz integral equations: one describes the external field, and the other describes the field inside the porous medium. The proposed method was validated through equivalent finite element method (FEM) simulations, and the results show that the pressure fluctuations predicted by the BEM agree well with those obtained from the FEM simulations. This paper presents numerical examples of struts with varying flow resistivity to investigate the impact of flow resistivity on the propeller-strut interaction noise. The results show that the sound pressure level (SPL) around the strut is significantly affected by the flow resistivity of the porous material, and this effect is highly dependent on the frequency. A comparison of predictions made using the method with experimental measurement results is provided to further substantiate the accuracy and reliability of the proposed method.