Calculation Of The Hydrodynamic Forces On A Slender Ship Oscillating In Shallow Water

During the design of modern ships, not only the performance of speediness is well designed, but also the manoeuvring and seakeeping properties are taken into discreetly consideration. In general, the manoeuvring and seakeeping properties are predicted mainly by experimental or numerical simulation. Better results can be measured via experiment, but it costs more money and work time. Numerical simulation is a method based on knowledge of fluid dynamics and computer technology, which can give a good prediction of manoeuvring and seakeeping properties, if the ship hull is known already. And this method is composed of viscous flow method and potential flow method. Viscous flow method and three-dimensional potential flow method cost a lot of computing time, while simple potential flow method such as strip method and slender body theory can give a fast prediction. The aim of the present work is to develop some simple programs to give a fast prediction of hydrodynamic forces relating to manoeuvring and seakeeping properties.The prediction of ship manoeuvring and seakeeping properties can be derived by calculation of the hydrodynamic coefficients of the moving ship. And the hydrodynamic forces are composed of wave force, radiation force and diffraction force. Only radiation force was dealt with in the present work. Generally speaking, the researches were mainly done while the ship was moving in deep water. However, for the modern and large ships, sailing in harbor and riverway, it cannot be seen as in deep water anymore. So it is also important to do the research work about moving ship in shallow water.The radiation forces on moving slender ships were calculated numerically. Based on the other researcher's work, some programs were developed in the present work, which can give a prediction of radiation forces when ship is moving in shallow water.This work is a numerical method which is based on the potential flow theory and slender body theory. By using the strip method, STF method and the 2.5D method to make up computer programs, the radiation forces of ships moving in shallow water were calculated. The two-dimensional hydrodynamic coefficients were obtained by simple Green function method, which can deal with complex ship hulls. Finally, a stable solution is obtained with Compaq Visual Fortran6.6. This computer program can solve the flow problem for arbitray shapes, which follow the assumptions of slender body.For the purpose of investigating the validity of the present method, the hydrodynamic coefficients of several kinds of ships such as parabolic hull, Wigley hull and Series60 are calculated and parts of the solutions are compared with the experimental results.This method costs less calculation time compared to the 3D method, but can give considerable results.