Slamming clustering on fast ships: From impact dynamics to global response analysis

In this paper the statistical properties of the slamming impact process are analyzed with the help of experimental data acquired in the towing tank on a high speed ferry model. The physical model is a segmented-hull with a flexible backbone-beam equipped, among other devices, with sensors to measure the wetness of hull sections and strain gauges to estimate the induced vertical bending moment. This setup allows us to analyze the slamming process not only on the basis of the detected slamming events but also on the basis of the whipping response produced by the impacts. Moreover, due to the particular model selected for the present analysis, characterized by a V-shaped hull, bottom as well as bow flare slamming contributions are investigated. One of the major findings is the evidence that the impact statistics are largely affected by the grouping of slams into clusters thus violating the hypothesis of mutual independence between successive impacts that is at the basis of most of the statistical models. The dependence of the whipping response on the impact velocity is also investigated. Finally, the definition of a new criterion for slamming identification based on the evaluation of the whipping bending moment is discussed

► A ship elastic model is tested in irregular sea to analyze the slamming occurrence. ► Slamming evens identified with Ochi criterion events show relevant clusterization. ► Slamming statistics are poorly described by theories based on event independence. ► The impact velocity and the peak of the whipping response are correlated but weakly. ► Slams can be identified by means of whipping if bow-flare events are considered too.