The effect of hull stiffness on ship slamming loads

Abstract

A mathematical model is developed to evaluate the effect of the hull girder stiffness on ship slamming loads. A two-degree-of-freedom spring-box system is used to model the ship's foward bottom where slamming occurs. The air region underneath the bottom plate is approximated by a one-dimensional, compressible inviscid flow, while the water region is governed by the Navier-Stokes equations describing the flow of an incompressible viscous fluid. Finite-difference methods were employed to solve the pertinent equations for the air and water regions. The equations of motion for the two-degree-of-freedom system were solved by the Wilson (theta) direct integral method. Free falling drop tests of scale models were conducted to verify, qualitatively, the analytical results. It was found from both the analytical and experimental results that the hull girder stiffness influenced the magnitude of slamming loads.