Shape-shifting skin to reduce drag on planes and subs:
It might seem counterintuitive to reduce drag by wrinkling the surface of a craft, but nature provides a precedent. “Dolphins induce their skin to wrinkle, so water won’t stick to them,” says Lagoudas.After calculating that this approach would work, his team tested designs for an “active skin” that shifts to the shape of an ideal surface wave.
One design uses “legs” just beneath the skin that lengthen under the influence of an electric field, bending the skin upwards. By controlling the field around each piezoceramic leg, Lagoudas’ team can deform the skin into corrugations of right wavelength and amplitude to cut down drag.
The corrugations can be at most 30 micrometres high. “We measured flow velocities very close to the skin and derived the skin friction drag — we have seen reductions as much as 50%,” says researcher Othon Rediniotis.
(Hat tip à mon père.)