New developments in vibration reduction with actively controlled trailing edge flaps

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This paper describes new developments in vibration reduction with actively controlled trailing edge flaps (ACF). This approach is applied to two different problems: 1. vibration reduction at high advance ratios, and 2. alleviation of vibrations due to blade vortex interaction (BVI) at low advance ratios. For the first problem, a new aeroelastic model incorporating trailing edge flaps and a new two-dimensional unsteady aerodynamic theory accounting for compressibility and unsteady freestream effects is used to study three different ACF configurations. For the second problem, BVI at low advance ratios is considered. For this case, a different aeroelastic response model was developed by combining a finite element model of the blade, incorporating an actively controlled flap, with a free wake aerodynamic model. It is shown that the two classes of problems have some fundamental differences. Results indicate that the actively controlled flap has remarkable potential for reducing 4/rev vibratory hub shears and moments for both classes of problems.