Piezoelectric and electromagnetic solutions aimed at realizing an active Gurney flap

Abstract

Gurney flaps are small devices whose dimensions are usually percentage units of the airfoil chord. A Gurney flap can change the flow field in the region of the trailing edge by introducing two contra-rotating vortices behind the flap, therein altering Kutta’s condition and circulation. This helps avoiding flow separation and moves stall occurrence to higher angles of attack. Active rotor technologies would, for instance, enable a helicopter to operate at reduced rotor tip speed while preserving flight performance capabilities. This article shows some results carried out on different, original, and feasible solutions, aimed at realizing “smart” Gurney flaps for rotorcraft blades. In particular, piezo patches, piezo stacks, and electromagnet-based solutions were exploited finding that only the last two solutions are able to satisfy specs. The last one (electromagnets) performs better from the viewpoints of implementation, cost (one order of magnitude), weight (less than 100 g with respect to 150 g of piezo stack), and power consumption (5 W with respect to 50 W).