Numerical Study On Unsteady Hydrodynamic Interaction Between Ships

Manoeuvrability is one of the most important hydrodynamic performances of ships, which has received more and more consideration for its close relationship to navigation safty. The increasing number of ships because of the rapid development of shipping leads to a high density of ships in waterways, so that the distance between ships become smaller and the ship motion relative to adjacent one become unavoidable in restricted water. When two ships sailing closely, the flow around them will be affected by the interaction between them. Additional lateral force and yaw moment generated during this process will have an impact on normal steering operation. As the ship dimensions become larger, most of the navigation areas appear to be narrow and shallow compared with ship dimensions, and may be regarded as the so-called restricted water. Because of the effect of the bank and water bottom, the hydrodynamic interaction between ships will be amplified obviously. The manoeuvrability problems due to these factors will have a significant influence on normal navigation, may even lead to a casualty if seriously. During the last decade, more and more attention has been paid to the maritime safety and ocean environment protection. Therefore, accurate prediction and investigation of hydrodynamic interaction between ships in restricted water become very important.In this thesis, the commercial CFD software FLUENT is used to study the hydrodynamic interaction between ships numerically. By solving the RANS equations, the unsteady viscous flow around two ships moving relatively on parallel courses in restricted waterway and the hydrodynamic interaction are calculated. UDF is compiled to define the relative motion of ships. Meanwhile, grid regeneration is dealt with by using the dynamic mesh method and sliding interface technique. The proposed method is verified by comparing the numerical results with experimental data. Then, by analyzing the numerical results obtained at different water depth, lateral distance between ships, ship length and ship speed, the influences of these factors on the hydrodynamic interaction are illustrated. At last, the influences of the bank, the current and the bridge piers on the hydrodynamic interaction are investigated numerically.The numerical method proposed in this thesis can qualitatively predict the ship-ship hydrodynamic interaction in restricted water. It can provide certain guidance on safe maneuvering and control of ships navigating in restricted water. The results presented in this thesis can also give a reference to further study of ship-ship hydrodynamic interaction problem under complicated conditions.