Rotor Blade Designs for Quiet Performance

CU Aerospace (CUA) and the University of Illinois at Urbana-Champaign (UIUC) are developing a new design methodology for rotor blades, which will offer quieter performance compared to conventional approaches. The applied approach seeks to mitigate the acoustic impact of vortex-induced noise of lifting rotors and propellers, which currently serves as a dominant noise source for these systems. The thrust distribution design methodology is guided to passively attenuate the roll-up process of rotor-tip vortices, which can lead to reduced interactions between shed vortices and subsequent blade elements or wing/body surfaces, as well as noise associated with turbulent regions outside of coherent vortex cores. Initial research has produced tailored rotor designs, in which the span-wise load was configured to produce similar lift to that of conventional designs, but with delayed roll-up of wake vortices controlled by eliminating strong discontinuities in vortex shedding strength along the span. The impact of such a design on rotor vehicle acoustics will be determined in proposed work.  The outcomes are anticipated to be of value to future electric VTOL and UAS development for Air Force missions where reduced acoustics signatures will be beneficial.  Potential commercial applications exist for improving public acceptance of rotorcraft for urban air mobility.