A Numerical Investigation of Ground Effect on a Coaxial Rotor System

This paper presents results of a numerical investigation into ground effect on a coaxial rotor system. The rotor system model comprises two n-bladed simply articulated, blade-element rotors with offset flapping hinges, feathering hinges and full-range angle of attack tabular airfoil data. The vortex ring method models the wake of each rotor in axial flow and an image plane represents the ground. A control law adjusts the cooperative and differential collective settings to drive the torques to equal but opposite magnitude while also achieving a desired thrust. The investigation reports the interactions of several important rotor parameters including disk loading, disk separation, solidity, twist rate and height above ground. When possible, the numerical results are compared to data in the open literature.