Alleviation of retreating side stall using active elements for helicopter rotors

Abstract

This paper presents CFD results for the performance of the W3-Sokol rotor in forward flight and the potential effect of the implementation of an active Gurney flap. A rigid blade was considered and calculations were conducted based on flight test data. The Gurney flap was extended from 40%R to 65%R and it was located at the trailing edge of the blade. The size of the Gurney was selected to be 2% of the chord based on previous study for the same rotor in hover, and the results were trimmed at the same thrust. The harmonic analysis of the flight test data proved to be a useful tool for identifying vibrations on the rotor caused by Blade Vortex Interaction and stall at the retreating side, and a carefully designed Gurney flap and actuation schedule were essential in order to control the separation of the flow.