Experimental Investigation of Propeller-Strut Interaction Noise

Abstract

This study presents an experimental evaluation of aeroacoustic noise generated by the interaction between a propeller and a downstream strut, a configuration representative of unmanned aerial vehicles. Experiments were conducted in the ALCOVES anechoic facility at VKI using far-field acoustic measurements and two-dimensional planar Particle Image Velocimetry (PIV). Far-field measurements show that tonal components associated with potential interaction decay with increasing axial separation and become negligible for separation distances greater than approximately 2.5 times the strut diameter. Broadband components, likely associated with viscous wake–strut interaction, persist across the full range of separation distances. Relative to the isolated propeller case, the presence of the strut leads to increased low-frequency broadband noise and haystacking around the blade-passing frequency and its subharmonics. The PIV measurements reveal spatially distributed tip-vortex impingement, together with vortex meandering and leapfrogging behavior, suggesting that unsteady wake dynamics contribute to the observed acoustic response. The results show that separation distance governs the relative contributions of potential and viscous interaction mechanisms, with specific attention to viscous wake-strut interactions.