Rotor wake and inflow characteristics of multirotor drone configurations

Abstract

A coordinated experimental and computational study of multirotor configurations has been carried out at low Reynolds numbers. The configurations include coaxial rotors, horizontally spaced side-by-side rotors, and tandem rotors separated by horizontal and vertical spacing, both. The calculations have been done at a nominal total thrust coefficient of 0.008. Although rotor performance, tip vortex trajectories, and flow velocity distributions are all of interest, the present study has focused on the inflow velocity field at a number of planes immediately above and below the rotor disks, for the express purpose of developing reduced order inflow models. Test data and the computations for the time averaged inflow and outflow fields compare well with each other. Significant rotor-wake interaction phenomena are seen due to the close proximity of the rotor disk, even when the rotors are in hover. Dynamic inflow coefficients have been extracted for representative strong rotor-vortex interaction scenarios.