Slippery interfaces for drag reduction

Abstract

AbstractInspired by natural interfaces with surprising transport properties, innovative modifications of surfaces have been engineered to reduce drag. The common theme across these new developments is the presence of lubricant patches or layers that decrease the direct contact of viscous liquid with non-slippery solid walls. For laminar flow, the traditional assumption regarding the lubricant layer is a constant shear rate or a steady pressure gradient, implying a net flow rate of the lubricant film. By challenging this assumption, Busse et al. (J. Fluid Mech., vol. 727, 2013, pp. 488–508) rigorously found that the hydrodynamic slip is reduced by the presence of a reversal of lubricant flow close to the wall. The analytical results for velocity field and change in drag provide insight into the optimal design of slippery surfaces with lubricant layers for drag reduction.