Assessment of CFD/CSD Coupled Aeroelastic Analysis Solution for HART II Rotor Incorporating Fuselage Effects

A loose coupling method is used to combine a comprehensive structural dynamics (CSD) code CAMRAD II and a computational fluid dynamics (CFD) solver KFLOW to correlate airloads, vortex trajectories, and blade motions with the HART II measured data. The computations are made using both isolated rotor and rotor-fuselage models, for the three test cases of the HART II rotor, in descending flight condition. A good agreement against the measured results has been obtained with the present models. It is found that the rotor-fuselage model improves the correlation significantly in terms of magnitudes and phases of the airloads solution. The blade-vortex interaction (BVI) peaks in the advancing and retreating sides of the disk are better captured, while the phase differences near the front disk area are greatly improved, with the inclusion of a fuselage. The reason of improvements due to the incorporation of a fuselage has been identified by investigating the induced velocity fields over the rotor disk as well as the vorticity distributions of a rotor at specified azimuth positions for both models. To clarify the issue, the trajectory of a vortex which leads to the BVI phenomena has been traced back from the formation to the final interaction location. Numerical results are presented to verify that a stronger upwash pattern over the front disk area and a reduced miss distance due to a fuselage play crucial roles of the improvements.