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A hybrid Navier-Stokes/free-wake solver has been employed to investigate the performance of a rotor equipped with a Gurney flap in steady level flight and in descent. A scaled model of the BO-105 rotor was studied. The calculations were coupled to a comprehensive analysis to properly account for the effects of the elastic deformations on the aerodynamic loads and to account for trim. Fixed and dynamically deployed Gurney flaps were considered. In forward flight, it was found that a properly chosen azimuthal deployment schedule of the Gurney flaps may reduce the peak-to-peak variations in hub loads, potentially reducing vibrations. In descent flight, it was found that the deployment of a fixed Gurney flap decreased the descent rate needed to maintain autorotation.

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This work presents progress on a detailed aerodynamic evaluation of Miniature Trailing-Edge Effectors (MiTEs) for active rotor control. We begin with a 2D computational fluid dynamics (CFD) study focused on establishing the dependency of MiTE effectiveness and performance upon basic geometric parameters on a VR-12 airfoil. The CFD study demonstrated that a MiTE placed at 10% chord upstream of the trailing-edge and sized at approximately 1% chord is capable of delivering moment coefficient increments of approximately ±0.03, or the same moment authority as a conventional flap moving ±2.3 degrees. Wind tunnel experiments were performed on a model blade section equipped with an operational MiTE in order to validate the CFD results, and strong agreement was shown. Finally, a small set of 3D unsteady CFD simulations with prescribed blade motion of a rotor equipped with MiTEs were performed. Under high-thrust, moderate speed conditions, MiTEs deployed sinusoidally at 4/rev frequency were capable of reducing 4/rev integrated aerodynamic loads in the vertical direction by approximately 80%.

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