EFFECT OF AIR LUBRICATION METHOD ON FRICTIONAL RESISTANCE REDUCTION OF SHIP

Abstract

Air lubrication method is a method in that air bubble is introduced into the turbulent boundary layer developing downstream along the solid surface in water flow. Effect of air lubrication on reducing frictional resistance is proved from the experiment results. Obtained results show that maximum total resistance reduction can be reduced 11% in ballast condition and 6% in full load condition with the assumption that thrust deduction is constant for with and without bubble injection. Effect of air bubble in reducing frictional resistance persists for the whole bottom area. Reduction rate of shear stress under the bottom of ship seems to be larger up stream and smaller toward the side of the ship. The mean propeller inflow velocity is increased for with air lubrication from no air condition due to the viscous resistance reduction. Estimation of wake fraction or advance speed of propeller based on viscous resistance reduction when bubble was injected is also considered.