Simulated flowfields in near-ground operation of single- and twin-rotor configurations

Numerical simulation with Navier-Stokes (N-S) equations is carried out for studying the flowfields of single, tandem, side-by-side, and coaxial rotors operating near the ground at low flight speeds. Source terms are introduced into the N-S equations to represent the rotor blades; therefore, only the flow scales of rotor far wake and ground boundary layer need to be resolved. Calculated results reveal the complex ground vortex phenomena produced by the interactions between the multiple wakes, the ground plane, and the incoming freestream. The effects of advance ratio, height above ground, as well as the rotor configuration, are analyzed.