The decrease of ship resistance is one of the most effective way to reduce operating costs and CO_2 production. The wave making resistance and form drag can be reduced by optimizing the hull form, but the frictional drag remains proportional to the wetted surface. The use of air as a lubricant in order to reduce that frictional drag is an active research topic and three techniques are identified: injecting air bubbles in the boundary layer, the use of air films along the bottom plating, and using air cavities in the ship's bottom. These approaches are the research topic for the Dutch joint-research project PELS and the EU project SMOOTH, both of which have the goal of not only predicting energy savings using numerical models and model tests, but proving it using full-scale demonstrator ships adapted for air lubrication. Although decreases in frictional resistance of nearly 20% have been obtained on model-scale ships, experience shows that the implementation of air lubrication can also easily increase the resistance of a ship.
展开▼
