Superhydrophobic Drag Reduction for Turbulent Flows in Open Water

Trapping air under water, superhydrophobic surfaces on boats have long been coveted for hydrodynamic drag reduction without bubble injection. Despite many reports of drag reduction in lab tests, such surfaces have not been successful in real-world tests on open water, at high Reynolds numbers. The authors develop hydrophobic microtrenches that provide a large slip, with a subtle detail that maximizes air retention. Replacing a portion of a motorboat's hull with the developed surface, they obtain large drag reduction under high-speed flows on the open sea. This has significant implications for energy efficiency in oceanic shipping.