aerodynamic performance prediction of an eVTOL hexacopter via a coupled BEM-RANS trim methodology
Loading...
Date
2026-10-13
Authors
Βανταράκης, Σπυρίδων
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
An essential step in the preliminary design phase of multirotor eVTOLs is the assessment of their aerodynamic performance in forward flight, which requires knowledge of the flight conditions, that is, its trimmed state: the attitude and rotor speeds at which forces and moments balance. This state is not known in advance, as it depends on the very loads and the rotor-rotor and rotor-airframe interference that are to be assessed. This thesis presents a methodology that recovers it by coupling a blade element momentum (BEMT) model with Reynolds-averaged Navier–Stokes (RANS) simulation, for fixed-pitch multirotor vehicles and it is applied here to a hexacopter design proposed by team ELEVATE Delft for the GoAERO Prize.
The BEMT model, which includes tip-loss, rotational-augmentation, post-stall and skewed-inflow corrections, is validated against wind-tunnel data for the NACA 5868-9 propeller. In the RANS solutions the rotors are represented by vbmSource, an actuator disk method, adapted from literature for Openfoam v2406. It is compared with BEMT for an isolated rotor and used to characterise rotor–body and rotor–rotor interference in cases of increasing completeness, to a simplified model of the vehicle. In the coupled procedure, BEMT solves the trim problem for the pitch angle and rotor speeds, and corrections formed from each RANS solution are fed back until the trimmed state stops changing.
At 25 m/s the hexacopter converged to a forward pitch angle of about 8.4°, with per-rotor thrust corrections of a few percent. The result is the vehicle's flight condition together with a converged CFD solution at that state which provides the basis for aerodynamic evaluation and for structural, propulsion and control-system design.
Description
Keywords
eVTOL design, Blade element momentum theory, RANS, Actuator disk, Trim