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Title: Flow control on helicopter rotors using active gurney flaps
Author: Pastrikakis, Vasileios
ISNI:       0000 0004 5352 0368
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2015
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This thesis presents closed loop control of active Gurney flaps on rotors. Firstly, it builds on the Helicopter Multi-Block 2 CFD solver of the University of Liverpool and demonstrates the implementation and use of Gurney flaps on wings, and rotors. The idea is to flag any cell face within the computational mesh with a solid, no slip boundary condition. Hence the infinitely thin Gurney can be approximated by “blocking cells” in the mesh. Comparison between thick Gurney flaps and infinitely thin Gurneys showed no difference on the integrated loads, the same flow structure was captured and the same vortices were identified ahead and behind the Gurney. The results presented for various test cases suggest that the method is simple and efficient and it can therefore be used for routine analysis of rotors with Gurney flaps. The potential effect of a Gurney flap all over the performance of the W3-Sokol rotor blade in hover was studied next. A rigid blade was first considered and the calculations were conducted at several thrust settings. The Gurney flap was extended from 46%R to 66%R and it was located at the trailing edge of the main rotor blade. Four different sizes of Gurney flaps were studied, 2%, 1%, 0.5% and 0.3% of the chord, and the biggest flap proved to be the most effective. A second study considered elastic blades with and without the Gurney flap. The results were trimmed at the same thrust values as the rigid blade and indicate an increase of aerodynamic performance when the Gurney flap is used, especially for high thrust cases. Moreover, the performance of the W3-Sokol rotor in forward flight with and without Gurney flap was tested. Rigid and elastic blade models were considered and calculations were guided using flight test data. The Gurney flap was extended from 40%R to 65%R, while the size of the Gurney was selected to be 2% of the chord based on the hover study. All results were trimmed to the same thrust as flight tests. The harmonic analysis of the flight test data proved to be a useful tool for identifying vibrations on the rotor caused by stall at the retreating side, and a carefully designed Gurney flap and actuation schedule were essential to alleviate the effects of flow separation. The last part of the thesis is dedicated to a closed loop actuation of the Gurney flap based on the leading edge pressure divergence criterion. The effect of the Gurney flap on the trimming of a full helicopter model, as well as the handling qualities of the rotorcraft were investigated. To the author’s knowledge this is the first attempt to study the effect of active Gurney flaps on elastic rotors with 3D CFD in a closed loop control for retreating blade stall alleviation and hover performance enhancement. The idea is that Gurney will stay deployed during the hover and it will be actuated based on the forward flight demands in order to enhance the rotorcraft capabilities.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TL Motor vehicles. Aeronautics. Astronautics