Influence of large hull deformations on the motion response of a fast catamaran craft with varying stiffness

Abstract

A hydroelastic study of a deformable catamaran is presented. Two-way coupling has been implemented between a RANS (Reynolds Averaged Navier-Stokes) multiphase finite volume flow solver and a finite element method for a highly flexible hull structure. The presented cases consider the hull is advancing at a constant speed in head waves. Different levels of stiffness are tested and deformation time series are recorded. Simulated motion response appears to be very sensitive to the stiffness of the hull which is responsible for a steady and unsteady structural deformation. The deformable hull does not help improve vessel motions. The largest deformations occur at the transom.The bow and the aft part of the boat acquire a combination of permanent and dynamic deformations. Both of them have the same effect, a variation of the effective length of the boat. As a consequence of the shortening of the hull the pitch restoring moment and the heave resorting force will be reduced. So there will have to be bigger heave and pitch movements to compensate similar forces.