Drag Reduction Effect and Wettability of Surface with Dual-Length Micro-Pillars

Abstract

We studied the drag reduction effect and wettability of surfaces with microscale cylindrical pillars. As the ideal surface that satisfies these two antinomy conditions, improvement of drag reduction effect and maintenance of air layer, we propose the microstructured surface with dual length pillars. Pillars are partly made shorter (a half of original ones) so that the pillars are arranged densely while the liquid solid contact at the tip of pillars is reduced. Test surfaces with dual-length pillars demonstrated greater drag reduction (over 10%) compared to a surface with uniform length pillars. We also examined the temporal variation of area of air layer retained on the tested surface that was exposed to water with or without flow. The dual-length pillar surface demonstrated better durability against wetting compared to that without short pillars.