Impact Loads on Ships From Breaking Waves

Abstract Plunging breaking waves may cause large impact loads on ships. Neither the risk of such impacts nor the magnitude of the resulting loads is much studied or well understood. Breaking waves in open sea typically occur in steep non-stationary growing sea-states. Recent advances in modelling of highly nonlinear wave conditions combined with computational fluid dynamics provide a means to quantify the frequency of breaking wave events. A higher-order spectral wave model is used to initialize large-domain wave propagation analyses in OpenFOAM. Breaking wave events are identified, and the risk of hitting different part of a vessel’s hull is evaluated. This includes evaluation of relative motions between the ship and breaking wave profile. Calculating linear vessel motions using a linearized wave field provides a good approximation compared to including the vessel in the CFD calculations. The focus is on beam-sea waves impacting the side of the ship. Existing rules and design practice account for dynamic wave loads but not large impulsive loading outside of the area vulnerable to bow-or stern slamming loads. A calculation framework is established that can be used to quantify how the risk of excessive loads depends on sea-state characteristics and vessel operation. General observations are made about the risk for high impact loads from breaking waves, and mitigating actions are discussed.