Numerical study on interference effects and wetted area pattern of asymmetric planing catamarans

Abstract

Asymmetrical planing catamarans are increasingly used in moderate to very high-speed applications due to some tempting qualities such as less wetted surface and better seakeeping behavior. The present numerical study attempts to provide new insight into hydrodynamics of such vessels by highlighting the distinguishing aspects and employing novel appropriate approaches to deal with them. A systematic investigation has been carried out on a prismatic geometry at various demihull separations (including zero separation, that is, symmetric monohull) and different trim angles in a wide range of speed coefficients, using a computational fluid dynamics solver. Obtained numerical results of steady-state resistance and lift forces are compared against different empirical methods. In order to offer an adequate explanation about the nature of forces and interference mechanisms, an analysis has been performed on viscous and pressure resistance components. Furthermore, the ability of the employed numerical method in estimation of wetted area pattern at the bottom of the planing hulls has been evaluated to provide explanation for some observed hydrodynamic behaviors of the asymmetric planing catamarans. It is seen that a significant reduction is reached in wetted surface area of catamaran configuration in comparison with corresponding monohull.