Small-Scale Rotor Design Variables and Their Effects on Aerodynamic and Aeroacoustic Performance of a Hovering Rotor

Abstract With the increased prominence of multicopter micro-aerial vehicles, more importance has been placed on the aerodynamic and acoustic performance of these systems, as their small-scale and lower Reynolds number regime provide results that are different from full-scale rotors. A computational methodology was employed in order to study the aerodynamic and aeroacoustic performance from different small-scale rotors used in a multicopter configuration. Three rotor design variables (twist, taper, and pitch) were investigated in order to understand their influence on aerodynamic and acoustic performance of a hovering rotor. Variables such as rotor rotation rate and rotor radius were kept constant. Common aerodynamic performance metrics such as the ratio of coefficient of thrust to coefficient of power and figure of merit (FM) were used to assess aerodynamic hover performance of the designed rotors. Acoustic performance was assessed by recording acoustic pressure in the far-field at two separate receivers. Acoustic results are presented in the frequency domain as one-third octave band data and as overall sound pressure level (SPL). Flow fields and pressure contours were calculated and displayed in order to help explain aerodynamic and acoustic results. From the results, insights are provided for rotor designs that are more aerodynamically and acoustically efficient in hover. Specifically, rotors that provided lower values of disk loading and higher values of power loading were typically more acoustically efficient. Using greater rotor twist and taper increased both aerodynamic and acoustic performance.