Mid-fidelity numerical investigation of the interactional aerodynamics mechanisms in an electrical vertical take-off and landing lift + cruise aircraft

This paper presents a comprehensive investigation into the aerodynamic interaction mechanisms occurring in a Lift + Cruise electric vertical takeoff and landing aircraft aimed to establish comprehensive knowledge of the flow physics related to an open-geometry reference aircraft and guide the preliminary design of novel Urban Air Mobility vehicle concepts. With this aim, a mid-fidelity aerodynamic solver was employed to evaluate the performance of the isolated rotor and subsequently used to capture the complex interactions between the propulsion system and the airframe at the full-vehicle level. Two Lift + Cruise concepts, equipped with four and eight propellers arranged in three different layouts, were investigated and compared in terms of both performance and flow fields for both hover and climb flight conditions. The study reveals that vertical rotor staggering, specifically with front and rear rotor disks, respectively, below and above the wing, significantly enhances thrust in both hover and climb flight conditions, leveraging beneficial wing-wake interactions. While mid-fidelity tools like DUST effectively capture these complex aerodynamic trends, the eight-rotor configuration shows higher interference levels due to fuselage proximity. Ultimately, these performance gains come with a trade-off of increased flow unsteadiness, which poses potential structural and acoustic challenges for Lift + Cruise aircraft design.