Development of a Floating Dock Numerical Model and the Ballast Water Distribution Strategy

Abstract

Abstract This study aims to develop a time-domain numerical model for simulating the dynamic response of a floating dock and propose a ballast water distribution strategy to help the dock reach a target draught with zero heel and trim. The floating dock is modelled as a six-degree-of-freedom (6-DOF) rigid body subjected to hydrostatic and hydrodynamic loads. A hydrostatic force model is built using Archimedes law and strip theory along the dock’s longitudinal direction. A hydrodynamic force model is made based on the effects of added mass and dynamic damping. The developed model is verified against the corresponding results obtained using HydroD, Autodesk Inventor and the theory of the dock’s free motions of heave, roll and pitch without damping. The ballast water distribution strategy provides the target water volumes in ballast tanks for a given draught and is created based on the equilibrium equations of draught, heel and trim. Vent pipes are installed in the ballast tanks to connect the air inside the tanks to the atmosphere outside the dock. Air cushions induced when the ballast water levels are higher than the bottoms of the vent pipes make the actual ballast water volumes not exceeding the target ballast water volumes at the maximum draught during ballasting operations. The relationship between the target ballast water volume and the height of the vent pipe bottom is investigated. In the case study, the freely floating processes of the dock with the ballast water distribution plans for different target draughts are simulated using the developed numerical model. The time histories of the dock’s draught, roll and pitch motions show that the proposed ballast water distribution strategy works successfully to make the dock reach its target draught with zero heel and trim. The maximum draught of the dock with the proper ballast water distribution and the corresponding vent pipe bottom heights in all ballast tanks are obtained.