Interference Resistance of Multi-Hull Vessels in Finite-Depth Waters

As high-speed ferry traffic is growing in near-shore areas, fuel efficiency of vessel operating in finite-depth waters becomes more critical. This can be achieved by introducing multi-hulls and minimizing the wave resistance by a proper configuration of the hulls. The wave resistance of thin-hulled vessels can be computed within Michell’s theory. Based on this principle, Yeung et al. (2004) introduced a formulation of the interference wave resistance on multi-hull vessels in deep water, after linearization of the boundary conditions. The method is generalized to any water-depth in this paper. Havelock (1921) derived the wave resistance of a single-hull vessel in finite-depth water. An expression of the interaction resistance between two hulls in finite-depth waters is derived, using a distribution of Havelock sources on the hulls. It is shown that the interference resistance may be defined as a function of geometric variables and a length-based Froude number and depth-based Froude number. The effect of sub-criticality, criticality and supercriticality of depth-based Froude number on the interference resistance is explored. The computation of the total wave resistance of two hulls is extended to vessels with any number of hulls. The application of this solution method is demonstrated. With the use of the formulation, multi-hull designs are optimized with respect to the geometric distribution of hulls as well as forward speed and water depth. The design of multi-hull vessels illustrates how an optimized design is quickly obtained. Design decisions early in the design process can therefore be facilitated by this procedure.