Passive Drag Reduction via Bionic Hull Coatings

摘要

The resistance of ships is often dominated by friction between the hull and the water. This study explores possibilities of reducing skin-friction drag in a way inspired by dolphins. These possess a soft skin believed to diminish drag by delaying the transition from laminar to turbulent flow. The underlying mechanism builds on a stabilization of the laminar boundary layer by the compliant surface. To transfer this mechanism to ship hulls, coatings similar to dolphin skin have been designed numerically, made from polymeric materials, and tested in a water tunnel. For the best coating, a drag reduction by almost 3% has been predicted in the boundary layer along the hull model of a small search-and-rescue vessel. The trends of the numerical predictions have been confirmed in the experiments.