A Comparison of High-Fidelity Simulation Approaches for eVTOL Rotor Flows in Descent Conditions

There is a significant interest in operating electric vertical take-o and landing (eVTOL) vehicles in complex urban environments, and thus, there is a need to understand how eVTOL rotors perform at steep descent rates. In descent, a complex flow state can arise near the rotor which requires a thorough analysis. This work employs high-fidelity numerical simulations. Specifically, two approaches are considered: blade-resolved DDES (i.e., BR-DDES), and actuator line model/ALM-based LES (i.e., ALM-LES). The goal of this paper is to compare results from these two approaches at various descent conditions. Three descent regimes/cases of high-speed (windmill brake state), lowspeed (vortex ring state), and very low-speed are studied. Overall, both approaches show a good agreement for all three cases, however, some differences are also observed between the two approaches, e.g., mean thrust is found to be different by up to 13%.