Numerical prediction of green water loads on ships

Green water loads are loads due to water taken onto the fore deck of the ship when it sails, or is moored, in heavy seas. Excessive loads have resulted in severe damage on for instance floating production,storage and offloading units (FPSO) and container ships. The present industry approach in predicting green water loads is to carry out model tests, being both time consuming and expensive, and on the basis of those to establish empirical relationships which are used in design.
The objective of the present Ph.D. project is to simulate numerically the dynamics of both the ship and the water at instants of high green water load, and hereby gain better understanding of the underlying processes. This is considered to be a step forward in establishing better tools for the design of safe ships and FPSO's.
In the present context, the dynamic problem to be solved will be addressed by applying the Navier Stokes solver NS3, which has been developed at ICCH (International Research Centre in Computational Hydrodynamics). The fluid domain will be discretized with optionally time-dependent curvilinear multiblock grids, which are adapted to the ship boundaries. These boundaries include the hull surface and the deck. The free surface will be treated by use of a VOF method, or similar procedures (level set method, marker density method), developed at ICCH to a preliminary level for wave breaking in the coastal environment. The study has some freedom in the choice of numerical methods, requiring basic tests of different possibilities in order to choose the optimal methods. For validating the basic numerics as well as to verify the validity of the numerical approach, in general, simple two dimensional problems will be solved with careful comparison with available data. In order to be able to impose both proper initial conditions and boundary conditions, the ship as well as the wave kinematics will be analysed.