Second Order Effects in Extreme Waves and Shallow Water Waves

This paper describes an analytical model to calculate the second order effects in waves with and without current. The model is based on a second order quadratic transfer function and a Lagrangian transformation for the effect of current. The method is validated against basin experience in shallow water with a large number of wave probes through the basin. The wave signals are separated in incoming and refelected bound and free waves based on the phase differences between the wave probes. The resulting separated bound wave shows good comparison to the set-down calculated with the analytical model. The second order method is further applied in the SAFE-FLOW Joint Industry Project to describe the steepness of extreme waves which can induce extremely large impact pressures on the hull of moored ship-type offshore structures.