- Greenwater damage to offshore structures results from high pressures and dynamic loads that occur when wave crests inundate the structure far above the waterline in areas not designed to withstand such pressures. In the present study, a Navier-Stokes method has been employed in conjunction with a level-set interface-capturing method for the prediction of slamming forces and green water on offshore platforms. The governing equations are formulated in curvilinear coordinate system and discretized using the finite-analytic method on a non-staggered grid. For the additional level set equations of evolution and re-initialization, we use the 3rd-order TVD (total variation diminishing) Runge-Kutta scheme for time derivative, and the 3 rd-order ENO (essentially non-oscillatory) scheme for spatial derivatives. The present method was validated first for the impact pressure prediction in a sloshing LNG tank. Simulations were then performed for the slamming of a 2D half-cylinder and a 3D hemisphere to illustrate the capability of the present method to deal with complex free surface flows involving relative motions between different computational blocks. The level-set RANS method was then employed for time-domain simulations of 2D and 3D offshore platforms in a numerical wave tank. Both The wave runup and greenwater on the platform decks were successfully predicted. Copyright 2007 by International Society of Offshore and Polar Engineers(ISOPE).