The hydrodynamic forces exerted on a semi-circle crosssection cylinder with flat top oscillating vertically across the free surface were numerically investigated. The flow field was divided Into top region (Inner flow field) where it is described by nonlinear shallow water wave equations and outer region where the flow field was solved by Yeung's close-fit method. These two regions are matched at their common boundaries where normal velocities and water exchange quantities between two regions must be unique. For satisfying above matching condition, computations with Iterations were taken The whole computation was developed In time domain.
Strip theory, e.g. STF method, is traditionally used to predict ship motions In wave and wave loads exerted on the hull. For the heavy sea conditions, ship will be possibly oscillating across the free surface which result in deck water phenomenon. Hodges and Webster (1986) measured experimentally the forces on a slightly submerged cylinder, and showed the observed flow patterns on deck Newman et al (1984) computed theoretically the added mass and damping coefficients of rectangular bodies close to, but still under, free surface In the frequency domain In his computation, the common boundaries (edges of deck) are considered as fluxes. In the present work, a semi-circle cylinder which is forced oscillating across the free surface was taken into account. The flat top of body is initially coincide with undisturbed free surface, and oscillating amplitude is small enough that the resulting disturbances to outer fluid region is small, so, the linear close-fit method (Yeung, 1982) IS available there And there will be only a very thin layer of water on the flat top of the body, whose motions can be considered as governed by the nonlinear shallow water wave equations, which can be solved by Glimm's random choice method (Dillingham, 1981). Both of them are matched on their common boundaries.