ABSTRACT

Air Circulating Tanh (ACT) is a system to drastically reduce the frictional resistance by air accumulated in the tanh installed in a ship's double bottom. The difference of the system from the air lubrication system using micro bubbles is no need of additional energy for injecting continuous air supply. The tanh must be designed to mahe the air−escape minimum by generating a circulating flow of the air in the tanh by the frictional force of the bottom water flow of the ship. In the present study, a very wide and shallow−draft ship is selected to get a large drag reduction effect by the ACT. In the present research project, the ACT is installed in the double bottom of the scale model of a 200m ship. CFD calculations are carried out to understand the characteristics of the generated air−circulation in the ACT and the generated waves on the boundary between air and water. On the basis of the CFD results, an ACT has been developed, and model experiments to measure the resistance acting on the ship are carried out to hnow the effects. Finaly the scale effect of the ACT is investigated by using CFD.