Modelling of Elastic Ship in Waves

Abstract: Ships in the seas undergo different distortions like bending, twisting or combined bending and twisting. The demand for increase in length and speed of the ships is increasing due to this the study for flexibility of structures is becoming important. Usually the structural excitations or natural frequencies of structure are given less priority since the natural frequencies of the structure are higher than encounter frequencies but since the length and speeds are increasing the encounter frequencies are closer to the fundamental frequencies. The structural behavior can be analyzed by semi-empirical formulation developed by classification societies but the flexibility of its application is limited. The present thesis work deals with the vertical motions of the ship structure. The thesis work is divided in to two parts the first part deals with the literature review of the global loads and Hydroelasticity and the second part deals with the modeling of the structural dynamic problem. In the modeling part Hydro-elasticity theory proposed by Bishop and Price on Euler Bernoulli beam is used for solving the structural dynamic problem and the illustration of springing and whipping is presented. An attempt has also been made to study the dynamic structural responses for a particular hull with the hydrodynamic forces and added mass from high speed strip program developed at KTH and the study has been performed to analyze the influence of various parameters like added mass, damping and stiffness.