Experimental tests and Numerical analysis for an Air Cavity Yacht

Each moving object in the earth or the principal industrial processes or simply the daily activities of humans involve the use of some kind of fluids. This interaction can be advantageous or disadvantageous. The deep knowledge of the main features of fluid flow allows to manage it with great advantages in terms of efficiency and sustainability, principally when the problem is the reduction of the resistance during the movement of a body.In the case of naval engineering, there is a strong interaction between the fluid and the ship. This interaction leads to a different effects, the most important one is the resistance during the navigation. The resistance of a ship is composed by two principal components: frictional resistance and wave resistance. Both of them must be reduced in order to keep the resistance low. The wave component is strongly dependent by the shape of the hull, so in preliminary phase, is possible to find, with different techniques, the better shape for reducing it. More complex is the reduction of the frictional component, because it depends on the contact between the surface of the ship and the water. The most difficult problem is the reduction of this component with methodologies applicable on the ships. There are many examples of drag reduction on flat plate, for example application of particular coatings or particular geometry but these passive methods are not suitable for the application on the ship. Another way is the injection of the air under the hull, this condition allows to separate the surface of the ship from the water. There are many examples of application of this method on flat plate models or on displacement hulls. This method seems the most promising one. These studies show that the injection of the air with a stable layer of air allows to reduce the frictional resistance.