Blade-Vortex Interaction Wave Radiation Patterns of Helicopter Blades with Different Leading-Edge Geometry

A simplified wave propagation model of Blade-Vortex Interaction (BVI) is developed and is used to predict regions in space where in-phase acoustic radiation occurs. The mathematical model (and associated computer code) present graphical images of the BVI wavelet accumulation process for observers located in both in-plane and out-of-plane positions, fostering a better understanding of the governing physics of the BVI noise radiation problem. Trace Mach number and simple unit impulse modeling (Level A) are used to demonstrate the importance of the phase of individual BVI interactions on relative levels of noise radiation. Blade sweep on the outer portion of the blade (forward and aft) and blades with serrated leading edges are shown to reduce in-phase wavelet accumulation and change the directivity patterns of BVI noise.