Abstract
A new method is proposed to mitigate ice accretions on wind turbine blades via the creation of a microstructural gradient surface geometry that facilitates spontaneous water droplet motion along the surface. The wettability gradients are formed by laser etching 35μm wide by 35μm deep channels into aluminum to form a surface with a gradually increasing solid area fraction which results in one end of the gradient surface being superhydrophobic and the other end being hydrophilic. Different design permutations are proposed and systematically assessed on the merits of their performance with respect to a baseline flat homogeneous surface and with respect to each other. An analytical model is also derived based on a balance of hysteresis and drag forces to predict the critical airspeed necessary for droplet movement as a function of the droplet size and the intrinsic contact angle of the surface. To date, experimentation has validated the model for the baseline surface and has also demonstrated that, in certain cases, up to 70% lower critical airspeeds are required to initiate droplet motion on these microstructured surfaces as opposed to the homogeneous baseline samples.
