Aerodynamic and Aeroacoustic Analysis of a Quadrotor Biplane Tailsitter in Forward Flight

Abstract

Unmanned aerial vehicles (UAV) with vertical take-off and landing capability have made significant progress in recent decades, especially with the emergence of advanced air mobility. One of the main issues these aircraft face that has challenged their commercial applicability is the high noise footprint. The aim of this study is to understand the complex aerodynamic interactions in such aircraft that lead to high noise emissions. For this purpose, a quadrotor biplane tailsitter was analyzed in forward flight conditions using computational fluid dynamics (CFD) focusing on the rotor-wing unsteady aerodynamic interaction, and its implications on the acoustic footprint of the aircraft. The aircraft was trimmed using the CFD data and blade element momentum theory estimates. The resulting surface pressure distribution was used to calculate the tonal and broadband noise footprints using the Ffowcs Williams - Hawkings equation and the Brooks, Pope, and Marcolini (BPM) semi-empirical model, respectively. The aircraft was analyzed with different rotor phasing arrangements to understand its effect on the noise footprint. The rotor-rotor interactions were found to be minimal due to the freestream. The rotor-airframe interaction leads to a substantial increase in aircraft noise. Rotor synchrophasing proved to be effective in controlling the aircraft noise footprint.