Helicopter Rotor Wake Investigations on a Wind Tunnel Model with Varying Blade Stub Lengths

Experimental and numerical investigations have been performed on a helicopter wind tunnel model for three rotor heads with different blade stub lengths. This investigation analyzes the origin and the development of the wake structures occurring from the various blade stub lengths and their interaction with the tail section of the helicopter to judge the influence of the blade stub spanwise dimension on drag, lift and pitching moment characteristics. Therefore, aerodynamic forces and moments and the wake flow fields are analyzed by experimental and numerical simulations. The origin of the distinct structures is identified by the numerical simulations. Specific cross flow planes in the wake captured experimentally the flow field and allowed a comparison with the numerical results. The numerical investigations are based on the unsteady Reynolds-averaged Navier-Stokes equations. The turbulence is modeled by the scale-adaptive simulation method and the rotation of the rotor head is modeled by the sliding mesh approach. The flow field of the experiment and the simulation showed good agreement and a detailed analysis of the dominant vortices propagating downstream is performed.