Turbulent friction drag reduction using electroactive polymer and electromagnetically driven surfaces

This work reports aerodynamic testing of two spanwise-oscillating surfaces fabricated out of electroactive polymers (EAPs) in the dielectric form of actuation, and of an electromagnetic-driven linear motor. Hot-wire and PIV measurements of velocity and direct measurement of friction drag using a drag balance are presented. A maximum of 16 % surface friction reduction, as calculated by the diminution of the wall-normal streamwise velocity gradient, was obtained. Among other quantities, the spatial dependence of the drag reduction was investigated. When this spatial transient and portions which are static are accounted for, the direct drag measurements complement the hot-wire data. PIV measurements, where the laser beam was parallel to the oscillating surface at y+ ≈ 15, support the hot-wire data. The two actuators are original in design, and significant contributions have been made to the development of EAPs. This experiment is the first to aerodynamically test EAP actuators at such a large scale and at a relatively moderate Re.