Loose Fluid-Structure Coupled Approach for a Rotor in Descent Incorporating Fuselage Effects

Abstract

A loose coupling approach is used to combine a comprehensive structural dynamics code CAMRAD II and a computational fluid dynamics solver KFLOW to validate the data and to identify the effect of fuselage on the aeroelastic behavior of the second higher harmonic rotor acoustic test rotor. The computations are made using isolated rotor and rotor–fuselage models. To demonstrate the effect of a fuselage, the shaft tilt angles remain identical for both configurations. A good correlation has been obtained with the present computational fluid dynamics/comprehensive structural dynamics method. It is observed that a rotor–fuselage model improves the correlation significantly in terms of magnitudes and phases of the airloads solution. All the blade–vortex interaction peaks are captured accurately, and the phase shift in the section normal forces improves significantly, with the inclusion of a fuselage. The sources of improvements are investigated, considering the vorticity distributions and induced velocity fields of a rotor. It is revealed that the upwash pattern due to a fuselage is not restricted locally but propagates to considerable portions of the disk. Numerical results indicate that the upwash is responsible to lift up vortices at the zone of interest for a reduced miss distance, which results in a stronger blade–vortex interaction for improved correlations.