Nonlinear Optimization Method of Ship Floating Condition Calculation in Wave Based on Vector

Ship floating condition in regular waves is calculated. New equations controlling any ship＇s floating condition are proposed by use of the vector operation. This form is a nonlinear optimization problem which can be solved using the penalty function method with constant coefficients. And the solving process is accelerated by dichotomy. During the solving process, the ship＇s displacement and buoyant centre have been calculated by the integration of the ship surface according to the waterline. The ship surface is described using an accumulative chord length theory in order to determine the displacement, the buoyancy center and the waterline. The draught forming the waterline at each station can be found out by calculating the intersection of the ship surface and the wave surface. The results of an example indicate that this method is exact and efficient. It can calculate the ship floating condition in regular waves as well as simplify the calculation and improve the computational efficiency and the precision of results.

A Multidisciplinary Method for Evaluating Ship Stability

The aim of this paper is to present the main results arisen from the joint efforts of the public-private partnership in being between CCII （Centro Cultura Innovativa d＇Impresa） of University of Salento and Apphia s.r.l.. This paper will focus on the results of the core of the OBSS （on board stability system） module that, starting from the exact 3D geometry of a ship hull, described by a discrete model in a standard format, the distribution of all weights onboard and the data acquired by the system, calculates ship floating conditions （in draught, heel and trim）. The proposed approach is based on geometry meshes represented by an universally accepted file format （named OBJ） first developed by Wavefront Technologies. Demonstration of the validity of the results is done by the authors using as hull model a simple rectangular box.

Stability of a tumblehome hull under the dead ship condition

Some methods for direct stability assessment under the dead ship condition were currently developed by the international maritime organization （IMO） under the Second Generation Intact Stability Criteria. Model tests and simulations are carried out to validate the numerical methods used in assessing the stability under the dead ship condition. This is done in three stages. Firstly, the uncoupled roll mathematical model （1 DOF） is adopted to calculate the roll motion based on the irregular beam waves and the steady wind. Secondly, a drift free experiment is conducted to measure the roll motion under irregular beam waves with zero speed, and then two restrained experiments with counter weights and four springs are performed under the same condition. Finally, the effects of the drift and sway motions on stability under the dead ship condition are then verified by experimental results, and the results of the numerical methods are compared to the results of the model experiments. It is concluded that more accurate numerical methods could be developed for assessing the direct stability under the dead ship condition.