A comparative assessment of vibration control capabilities of a L-shaped Gurney flap

This work presents the capabilities of a novel L-shaped trailing edge Gurney Flap as a device for vibration reduction. The primary effect of this L-tab is represented by a modification of the reference airfoil mean line shape through two counter rotating vortical structures created at the trailing edge. The comparison of the aerodynamic loads generated by the novel L-tab Gurney flap and a classical trailing edge flap, allows to estimate the ranges of reduced frequency where the L-tab is expected to perform better with respect to the trailing edge flap and viceversa. Linear aerostructural models for a typical section representative of helicopter blade equipped with a partial span L-tab or a trailing edge flap are built, and a higher harmonic control algorithm is applied. Performance are compared between the two devices to reduce separately the N/rev harmonics of the blade root rotating frame vertical force, flapping and feathering moments. The attainment of similar results with classical trailing edge device is a further confirmation of the potential feasibility of this novel L-tab as an effective alternative means for vibration reduction on rotor blades.

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