Investigations of Helicopter Wake Flow Including Rotor-Head Motion

Abstract

The present paper emphasizes on the characteristics of the wake flowfield emanating from a helicopter fuselage and rotor head, including cyclic and collective pitch motion. Predicting the convection of the coherent vortical flow structures generated by the fuselage as well as the rotor head is a difficult goal by the application of numerical methods. Furthermore, the accurate determination of the wake flowfield requires the detailed knowledge of the origin of the associated coherent structures. Therefore, numerical and experimental investigations have been conducted on a twin-engine light utility helicopter. The wind-tunnel model includes a fuselage and a rotating five-bladed rotor head. To obtain the wake flowfield, stereoscopic particle image velocimetry is applied. The numerical investigations are performed with a commercial flow solver. The flow solver is based on the unsteady Reynolds-averaged Navier–Stokes equations. Turbulence modeling is performed with the scale-adaptive simulation model. The motion of the rotor head is covered by the moving and deforming mesh methods. The wake-flow velocity distribution obtained by the experimental data and the numerical results shows a good agreement and allows a detailed analysis of the dominant vortical flow structures propagating downstream.