Flow Noise Reduction of Rotary-Wing UAV Using Tip Porosity

This study investigates the effects of tip porosity on tip vortex formation and noise generation for a rotor for small unmanned aerial vehicles (UAVs). The rotor-tip porosity reduces the strength of the tip vortex, causing it to dissipate rapidly. The shedding of weakened tip vortex appears to induce a reduction in tonal noise arising from the harmonics of the blade passing frequency. The tip-vortex mitigation by tip porosity results in a decreased turbulence intensity in the rotor wake, leading to a reduction in broadband noise.