Improved Conceptual Design of eVTOL Aircraft: Considering Rotor–Rotor Interactional Effects

Abstract Electric vertical takeoff and landing (eVTOL) aircraft equipped with a distributed electric propulsion (DEP) system have rotors positioned close to one another, leading to unsteady rotor–rotor interactions. These interactions are known to increase rotor aeroacoustic noise due to aerodynamic load fluctuations. Therefore, capturing the noise increase caused by rotor interactions is critical during the conceptual design phase of eVTOL aircraft. Low-fidelity rotor analysis models, such as blade element momentum theory (BEMT), which are commonly used in conventional conceptual design frameworks for their efficiency, fail to account for rotor–rotor interaction effects as they assume each rotor operates in isolation. In this study, a rotor aeroacoustic solver is integrated into the conceptual design framework, RISPECT+. Additionally, a new aerodynamic coupling module between two distinct aerodynamic solvers is developed to capture the noise increase from rotor–rotor interactions. In this module, rotor aerodynamic analysis results from the lower-fidelity model are corrected based on differences with the higher-fidelity model, enabling the capture of aerodynamic force unsteadiness and the resulting noise increase. Finally, this new framework is used to conduct sensitivity analysis and multi-objective design optimization, taking into account both gross weight and noise impact.