Application of passive flow control device on helicopter rotor blades

Abstract

Application of an efficient flow control system on helicopter rotor blades may lead to improved aerodynamic performance. Recently, the own invention of a passive vortex generator (Rod Vortex Generator - RVG) has been analysed for channel and wing flows proving its capability to reduce flow separation. The application of this passive flow control device on helicopter rotor blades is described in the present paper. The basic flow mechanism is based on the intensification of exchange of momentum in the direction normal to the wall by a streamwise vortex. High momentum air is transferred to the low momentum region close to the surface and therefore the separation bubble is reduced. The present CFD investigation was carried out with the FLOWer code from DLR which solves the Favre-averaged Navier-Stokes equations using the chimera overlapping grids technique and LEA (Linear Explicit Algebraic Stress) k-? turbulence model. The validation of the numerical setup for high-speed transonic hover conditions is based on a comparison with experimental data obtained by Caradonna and Tung (1981). For forward flight regime, the validation is based on a comparison with flight test data gathered by Cross and Watts for the AH-1G helicopter (1988). It has been proven that the application of the proposed flow control system reduces the size of the separation bubble increasing the aerodynamic performance in both states of flight.