Drag reduction on vessels and study on its viability /

Abstract

The most severe component in the resistance of a ship is the frictional one. As we know the source of this bare hull frictional resistance is the basic wave resistance and viscous resistance or drag. Drag as we know it is directly proportional to the area it acts upon. By reducing the frictional resistance through form optimization, and more viably and hence, more importantly, air lubrication, total resistance and so fuel costs can be decreased. Especially for existing ships, reduction of ship resistance by form optimization is difficult and not cost effective, but the application of air lubrication through injection methods like in the Mitsubishi air film injection study. Reducing the frictional resistance by air injection below the ship in combination with special coatings is an active area of research; anecdotally, performance gains are usually large. The paper gives an overview of some model scale and full-scale measurement results of ships. In this study, the air lubrication method is presented and the effect of air lubrication on resistance. The analyses are performed by a commercial code solving Navier-Stokes equations. The coefficient of frictional resistance of the ship is calculated as an equivalent flat plate of the ship’s wetted surface.