Trimmed Forward Flight Simulation with CFD featuring Elastic Rotor Blades with and without Active Control

EUROCOPTER showed as a world premiere in 2005 the proof of concept of an active flap rotor in flight on a BK117 prototype demonstrator. Since this very first flight, several test campaigns have been flown to investigate the efficiency of different control strategies with respect to noise, vibration and performance benefits. From an aerodynamic point of view the active blades with flaps in neutral position are very similar to the EC145 serial blades, from a dynamical point of view they differ significantly from them. Taking this into account two specifically aerodynamic objectives are investigated: first objective is to present the comparison of the used numerical modeling and simulation with flight test results for the passive rotor, second objective is to present numeric results achieved for the performance benefit of the active rotor with a pure 2/rev control input. For both objectives the so called “weak coupling” method between the Navier-Stokes solver FLOWer and the flight mechanics code HOST has been used to obtain a trimmed solution. The method is applied to the isolated rotor in steady forward flight conditions.