Numerical Simulation Of Green Water On Deck At Bow

When a ship is sailing in severe sea conditions, large amplitudes of relative motions between the ship hull and waves can result in a considerable amount of water pouring onto the deck from the ship bow, shipboards and even the stern. This phenomenon is green water on deck. Its negative influences include: violent impact and destruction of devices on the decks, voluntary or passive speed-loss, being forced to change courses, large influence on ship motions and interference of sailors’ sightlines. Serious events of green water on deck may cause major damage of ship hulls or even their capsizing. Most recently, experiments indicated that events of green water from shipboards could affect the parametric rolling motion of ships. For the reasons above, investigation of green water on deck is of great significance on ship structures, safety of crew and ship performance during the process of design of various ships.In addition, several documented accidents of shutdown and structural failure of FPSO(Floating Production Storage and Offloading) related to green water on deck demonstrate that the consideration of green water is also an important factor in the design of ship-formed offshore structures with zero speed.Based on a summary of previous research work, this thesis conducted, numerical simulations of green water on deck via solving incompressible NS equations by the solver naoe-FOAM-SJTU. The simulation includes the whole process of numerically generating and absorbing waves, large deformation of free-surface, direct coupling computations of the interactions between ships and waves, slamming on the deck and superstructures caused by green water events and wave breaking phenomena.This thesis started with thorough verification and validation of the capability of naoe-FOAM-SJTU on handling ship motions in waves, large deformation of free surface and the prediction of green water loads. Proper numerical schemes and models were then chosen through the detailed converge study and comparisons with experimental data. Both two and three dimensional simulations of both fixed ships and ones with degrees of freedom were presented in the following sections. The computational results were used to analyze the influence of green water events on ship motions and further demonstrated the necessity of direct coupling computations of green water events and ship motions. Then, through comparing with experiments, the following sections discussed in detail types of green water, the process of green water events and green water impact.