Nonlinear heave radiation forces on two-dimensional single and twin hulls

A study of nonlinear heave radiation of two-dimensional single and double h ulls has been carried out in the time domain. The problem is analyzed by me ans of a fully nonlinear mathematical model, referred to as the mixed Euler ian-Lagrangian (MEL) model, which is based on an integral relation formulat ion coupled with time-integration of the nonlinear free-surface boundary co nditions. The integral equation solver is based on a cubic-spline boundary- element scheme in which both potential and velocity continuity conditions c an be enforced through the intersection points. The body undergoes periodic forced heave oscillation. By implementing effective wave-absorbing beaches at the two ends of the rectangular numerical tank, long-term steady-state force-histories could be achieved consistently in all computations. Results in terms of radiation forces for rectangular and triangular single- and twin-hull geometries are presented and discussed. Linear hydrodynamic forces in terms of added-mass and damping are validated for the rectangular hull. The Fourier-analyzed results reveal the extent of nonlinear (higher- order) components in the force-signals over different parameters which incl ude the amplitudes of oscillation, hull-spacing for the twin-hulls and wate r depth. (C) 2001 Elsevier Science Ltd. All rights reserved.