Interactional Aerodynamic Effects on Rotor Performance in Hover and Forward Flight

A theoretical analysis has been conducted into the significance of rotor/body aerodynamic interactions on rotor performance and blade loads. Results from the analysis are compared with measurements from tests that were conducted on a rotor/body combination in hover and at advance ratios between 0.05 and 0.25. The experimental results showed significant changes in rotor thrust and power requirements with the introduction of a body to the flowfield. The theoretical analysis has been conducted to help explain the aerodynamic mechanisms involved. A fully unsteady potential flow model of the rotor and body was developed. The wake models consisted of a free-wake methodology, as well as a standard prescribed wake, both coupled with a novel treatment of the rotor wake/body interaction process. These wake models were combined with the panel and rotor models to allow fully interactive trim calculations. The theoretical analysis has shown significant changes in the inflow distribution through the rotor disk, as well as large associated changes in the lift and inflow distribution due to the presence of the body, and these results can be used to explain the source of the measured effects on the rotor performance.