On the aerodynamics of an electric vertical take-off and landing aircraft using lattice Boltzmann method

This study investigates the static stability and flow field of a cruising Electric Vertical Take-off and Landing (eVTOL) aircraft with a compound-wing configuration using Lattice Boltzmann Method (LBM). Numerical accuracy of Finite Volume Method (FVM) and LBM is validated and comparatively analyzed based on isolated-rotor simulations. The LBM-based simulations are 8–9 times faster than those based on FVM for weakly compressible flows, which exhibits a significant advantage in computational efficiency and cost. The maximum error of thrust is ∼ 11% for LBM-based simulations and that of torque is ∼ 7%, which is similar to that of FVM. Unsteady simulations based on LBM are conducted for the whole eVTOL aircraft, and flow field structures and static stability are further analyzed. The results reveal that four varieties of vortical structures dominate the flow field, including wingtip and root vortices, vortices generated by static lift rotors, and vortices originating from the counter-rotating tail-propeller pair, varying with angle of attack and angle of sideslip. Their developing mechanisms and mutual interactions are examined in detail. The aircraft is unstable in terms of longitudinal and directional static stabilities, while it is stable in lateral, enhanced by wingtip vortices. Moreover, tail-mounted propulsion places higher demands on thrust propellers. In addition, vortices generating at the leading edges of the upper lift rotors delay separation on the wing upper surface but imposes negative effects on both longitudinal and lateral stability. The high computational efficiency, accurate flow prediction, and realizable aerodynamic forces demonstrated by LBM provide engineering insight for future aerodynamic performance analysis and development of eVTOL aircraft.