A practical design approach including resistance predictions for medium-speed catamarans

Medium-speed catamarans are under development as a new class of vessels to meet requirements for highly efficient sea transportation with low environmental impact. Reduced service speed and increased deadweight will increase transport efficiency. Compared to current high-speed catamarans, these new vessels will operate in a transitional speed range between high-speed craft and conventional displacement ships. In this paper, design guidelines to choose appropriate main dimensions for medium speed catamarans with minimum resistance were derived and a preliminary design was made. These vessels will operate at Froude numbers of about 0.35 and have a relatively low prismatic coefficient of about 0.5 in conjunction with a small transom immersion. Different methods are discussed to correctly predict the calm water resistance, with RANSE (Reynolds-averaged Navier-Stokes equations)-based flow simulations being the most promising. It is shown that they are capable of predicting the hydrodynamic characteristics of medium-speed catamarans, such as drag force, trim and sinkage with acceptable accuracy