Investigation on Loading condition Effects to Duct-Type Energy Saving Device

Abstract

　A duct-type energy saving device is one of the effective devices for ships. Most of the kind of ducts are attached to the front of the propeller, which is widely used in actual ships. National Maritime Research Institute has also developed an energy saving duct, and it has been empirically found that the effect tends to be greater in the ballast condition than in the laden condition. The authors tried to clarify the mechanism of energy saving effect by using the data of nominal wake distribution and surface pressure distribution of a ship, because the flow field around the hull changes when the draft or trim varies depending on the loading conditions. As a result, we conclude that the thrust deduction coefficient and the wake coefficient of the self-propulsion factors change depending on the loading conditions, which are caused by the variation of the position of the vortex flowing into the duct.