Numerical studies on modeling the near- and far-field wake vortex of a quadrotor in forward flight

Abstract

The operation of Unmanned Aerial Systems (UAS) is expected to keep increasing in the future with its rapid advancement and ever-expanding applications. One of the safety measures that need to be put into place for safe UAS operations is separation requirements. This article presents the results from flow simulations of quadrotor propellers using the Overset method in ANSYS Fluent 19.2 and the Virtual Blade Model (VBM) method in OpenFOAM as part of ongoing work to establish a wake vortex–based safe separation distance for UAS operations. The near-field flow simulation using the Reynolds-averaged Navier–Stokes turbulence model was validated with mesh convergence and turbulence model studies and verified with simulation and experimental data in the literature to ensure that the propeller simulation methods could generate a realistic near-field flow of multi-rotor UAS in forward flight. The far-field flow simulation using the Large Eddy Simulation turbulence model was validated with a mesh convergence study by calculating and comparing the circulation strength of the vortices in the far-field flow of each mesh setup but not verified due to a lack of existing experimental data.

Comparison of Small Multirotor Wake Vortex of Different Weight Class and Rotor Configurations via Numerical Simulation

“…The boundary condition, turbulence model, and mesh setting were identical to those used in the validation and verification cases in Ref. [31] other than minor enlargement in sizing to accommodate the larger UAS. The RANS near field solutions, once converged, are mapped to the inlet patch of the LES domain to simulate wake vortex evolution over a set follow distance behind the wake generating UAS (see Fig.…”

“…A uniformly sized quad-grid domain was used with mesh density described in Ref. [31] with ∼ 50 million cells for the domain used for DJI Phantom 3; the mesh resolution are the same for the DJI Inspire 1 and DJI M600 cases but with enlarged domains.…”