Aerodynamic forces on high speed multi-hulled marine vehicles

The need for high-speed high-payload craft has led to a considerable interest in vehicles capable of bridging the gap between conventional ships and aircraft. One such concept uses the forward motion of the craft to create aerodynamic forces on a wing-like structure, and hence, alleviate the overall drag by reducing the wetted area. This research focuses on the use of suitably shaped multihull geometries to achieve e cient aerodynamic lift for high-speed sea vessels. The problem is rst studied in two dimensions using a simpli ed analytical approach and CFD modeling. The work is then extended into three dimensions and a nal aerodynamic model is produced for a complete hull form, including the e ects of hydrodynamic surfaces above the water. The aerodynamic analysis demonstrates that signi cant e ciency can be achieved through careful shaping of the side hull and cross deck, with lift-to-drag ratios of nearly 50 for a complete aerodynamic hull con guration. Further analysis is carried out using a hybrid vehicle stability model to determine the e ect of such aerodynamic alleviation on a theoretical planing hull vessel. Comparisons are made using the Savitsky planing model, and from this it is found that the resistance can be almost halved for a fty metre, three hundred tonne vehicle with aerodynamic alleviation traveling at 70 knots. A comparative study is made for the hybrid vehicle with regards to size, speed and weight, whilst attempting to match the proportion of aerodynamic lift with speed to a theoretical optimum. From this the likely con gurations for future development are identi ed.