A Simple Analytical Model for Investigation of Fuselage-Rotor Interference

A simple analytical model to account for fuselage-induced velocities at rotor blade elements and at rotor wake nodes is described. The method is applied to four different fuselage configurations: two rotor test rig bodies used in the NASA Ames Full-Scale Aerodynamics Complex and two test rigs used by the DLR (German Aerospace Center) in the Large Low-speed Facility of the German-Dutch Wind tunnels in the Netherlands. The fuselage-induced flow fields in the volume of rotor operation above the respective fuselages are modeled in the range of angle of attack and sideslip applicable in the respective wind tunnel of their usage. Results for the effect of the fuselage, relative to the isolated rotor, on trim controls and rotor thrust are estimated using the blade element/momentum theory, and are compared to results obtained with a comprehensive rotor code. It is found that in forward flight fuselage effects mainly affect the lateral control, strongly depending on angle of attack. The rotor thrust can be varied by the presence of the fuselage, depending on its angle of attack, and the fuselage influence generally increases with flight speed. In sideslip conditions, the fuselage influence on cyclic controls shifts from mainly lateral control in forward flight to mainly longitudinal control in quartering flight. Significant differences in results emerge from the method of data generation, depending on the representation of separated flow (Navier-Stokes code) or not (Panel code).