Random forces on a slender vertical cylinder given by high sea waves interacting with a current

This paper investigates the Morison force on a slender vertical cylinder, produced by random wave groups with large waves, either in an undisturbed wave field or for waves superimposed on a uniform current. For this purpose Boccotti's Quasi-Determinism theory is extended to wave-current interaction. Thus, assuming that a very large wave occurs at some fixed time and location for a fixed value of current velocity, the analytical expressions of the free-surface displacement and of the velocity potential are obtained. Finally, it is found that the maximum wave force given by the New Wave model, which is suggested by the API recommendations for the calculation of wave forces of sea waves on a structure, tends to underestimate the maximum total force given by the Quasi-Determinism theory.