Computational and Experimental Investigation of Quadrotor Aerodynamics and Aeroacoustics

Abstract

Aerodynamic interactions have a significant effect on quadrotor performance and aeroacoustic signature. Free wake methods allow the simulation of complex multirotor flows at a low computational cost, yet they were originally developed for simulations of full-scale helicopter rotors. The study aims to demonstrate the applicability of lower fidelity methods for predicting small-size rotors performance, also used as input for aeroacoustic computations. Another focus is to characterise the aerodynamic interactions that cause a considerable difference to the superposition of single rotors. Quadrotor configurations are investigated experimentally and numerically using solvers of different fidelity, including free wake methods and an URANS tool. The efficiency of a diamond configuration with non-overlapping rotor blades improves by 5% compared to four isolated rotors. The effect is pronounced for the nose-up rotor tilt with intensified interactions, for which the efficiency of the diamond configuration increases by 11% at the rotor spacing of 1.2 rotor diameters. In contrast, interactions in the square configuration are detrimental for all spacings with the optimum at blade overlap of 0.04 rotor diameters. Adding a vertical offset of the back rotors relative to the front rotors in the square configuration improves the quadrotor performance, while raising the rearmost rotor in the diamond configuration causes a decrease in its efficiency.