Turbulent Drag Reduction by Polymer Containing Paint: Simultaneous Measurement of Skin Friction and Release Rate

Abstract

Performance test for polymer containing trial antifouling paint was carried out experimentally. This trial paint is made by adding a polymer (PEO) to commercial antifouling paint for ship hull. Our developing paint has a function of leaching out the polymer and eventually reduces the skin frictional drag by the effect of dissolved polymer when the ship cruises. As the performance test, we examined the release rate of the polymer from the trial paint and measured the skin frictional drag at the same time. In addition, the velocity distribution near the painted wall was measured by Laser Doppler Velocimeter (LDV). As a result, in the first stage, the large drag reduction was obtained with releasing polymer. The Reynolds shear stress near the painted wall largely decreases comparing with the commercial antifouling paint in the water flow. However, after several hours, this drag reducing effect was hardly lost.