Modeling Multirotor Aerodynamic Interactions Through the Vortex Particle Method

Abstract

Distributed electric propulsion and vertical takeoff and landing has recently opened a new design space for urban air mobility. However, the use of multiple rotors operating in close proximity introduces complicated aerodynamic interactions that are not well understood, are not captured through conventional design tools, and need to be addressed in the conceptual design stage. This study investigates the accuracy of the viscous vortex particle method (VPM) in modeling rotor-on-rotor aerodynamic interactions in a sideby-side configuration as encountered in tilt-rotor, quadrotor, and distributed propulsion aircraft. The VPM approach has the potential to enable the use of mid/high fidelity models capturing multirotor interactions during conceptual design. Validation of the individual rotor is presented in both hovering and forward-flight configurations at both low and high Reynolds numbers. Validation of the hovering multirotor is then presented, followed by a detailed parametric study of rotor-to-rotor interactions during hover and forward flight, constructing the response surface of thrust, torque, and propulsive efficiency as a function of operational parameters.

Experimental Study of the Aerodynamic Interaction between Side-by-Side Propellers in eVTOL Airplane Mode through Stereoscopic Particle Image Velocimetry

“…Nevertheless, these solvers required a robust experimental validation, especially to evaluate their capabilities of accurately simulating the strong interactional effects that are typical of the flow fields of multi-propeller configurations. With this aim, Alvarez and Ning [14,15] reproduced the side-by-side propeller experiment in hover conditions conducted by Zhou et al [5] using a mid-fidelity aerodynamic VPM code and found a quite promising agreement in terms of flow-field representation.…”

Generic Design Methodology for Vertical Takeoff and Landing Aircraft with Hybrid-Electric Propulsion

“…where ρ and V ∞ denote the air density and freestream velocity, respectively. The interference drag due to thrusters' interaction is ignored because it affects the propulsive efficiency by less than 3% [31].…”

A Hybrid Non-Linear Unsteady Vortex Lattice-Vortex Particle Method for Rotor Blades Aerodynamic Simulations

“…The addition of a viscous effect enables the viscous VPM to model the vortex mixing and decaying that is crucial for complex dynamic simulations, such as the travel of vortex rings [29,30] and viscous flows with the presence of the wall and objects [36,37]. Furthermore, it led the way to the aforementioned hybrid schemes where viscous VPM is combined with panels methods [38][39][40][41].…”

“…Difficulties with a strictly connected wake of panels motivated the rotorcraft aerodynamic community to consider alternative wake representation, such as the VPM. One advantage of the VPM is that it can be mixed with any lifting surface modeling such as 2D blade elements [39], vortex lattice method [26,51] and the panel method [40,52,53]. VPM has proven to be a useful prediction tool for the wake representation of hovering rotors both in and out of ground effect.…”