Influence of an active Gurney flap upon the aerodynamic and performance properties of a main rotor in various states of helicopter flight

Abstract

In rotorcraft engineering the Active Gurney Flap (AGF) is a small tab located at lower surface of the blade near its trailing edge. The tab is oscillating perpendicularly to the blade surface. When deployed it deflects air stream behind the blade trailing edge downwards, leading to the lift increase. On the advancing blade, the AGF is retracted to minimise rotor torque. The AGF technology may improve the overall performance of a helicopter. However, to take full advantage of such potential benefits, it is necessary to gain knowledge about physical phenomena related to the AGF. This especially concerns determination of states of helicopter flight, in which the application of the AGF technology could be the most beneficial. Explaining such the problems was the main subject of the research presented in the paper. Computational simulations of the investigated phenomena have been conducted using the URANS solver. To simulate a motion of the AGF mounted on the rotor blades, the original methodology, based on computational-mesh-deformation approach has been developed and implemented. The presented computational results have concerned mainly simulations of full scale main rotor with blades equipped with the AGFs. Additionally, some quasi-two-dimensional studies, conducted in conditions similar as in a real flight, have been discussed too. The overall conclusion from the conducted computational studies is, that the greatest benefits of using the AGF technology on the rotor blades may be expected in states of helicopter flight characterised by higher values of the rotor thrust coefficient, especially when the retreating-blade dynamic stall occurs.