Abstract
A skin-friction reducing marine paint has been developed by mixing fine powder of PolyEthyleneOxide (PEO) with Self-Polishing Copolymer (SPC) Anti-Fouling (AF) paint. PEO is well documented as an effective drag reducing additive that exhibits the Toms effect. Friction drag reduction has been implemented by injecting aqueous polymer solutions into the turbulent boundary layer of liquid flows. However, such polymer injection is usually achieved through penetrations in the solid flow boundary, which is a significant practical obstacle to marine application. Here, we explore the use of a PEO infused marine coating to deliver the polymer molecules to the near-wall flow. The erosion mechanism of SPC paint resin and the subsequent dissolution of PEO lead to the controlled release of PEO from the painted surface. The direct force-balance measurement in a high-speed circulating water channel demonstrated a maximum 33% skin friction reduction relative to conventional AF paint. From local shear stress measurements the skin friction coefficient of the present paint was lower than that of a smooth, uncoated surface, thereby demonstrating the turbulence modification due to the polymer additive. From measurements in a tow tank, the skin frictional drag was found to decrease by approximately 10% compared with conventional AF paint.
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