Parametric Rolling of Ships – Then and Now

Abstract

Modern research on parametric rolling of ships was first conducted in Germany in the late 1930s. This work was initiated in an effort to explain the capsizing of some small ships such as coasters and fishing vessels in severe following seas. The work included experiments with models in open water as well as numerical and theoretical computations. The phenomenon was thought to be of concern principally in following seas and for small, low freeboard ships. In the 1990s, however, there were reports of containerships and even some cruise ships experiencing heavy rolling in head seas. These were ships having a hull form characterized by great flare forward and wide flaring stern sections, features that are known to lead to significant stability variations in waves. The APL CHINA casualty in October 1998 focused attention on parametric rolling in head seas. The investigation of this casualty included theoretical computations of GZ variations, model experiments and numerical simulations as well as meteorological studies of the wind and sea conditions prevailing at the time. Results of the investigation received wide dissemination in the technical press. Since the APL CHINA casualty and other similar incidents, much theoretical and experimental work has been focused on head seas parametric roll. IMO and many of the Class Societies now have recommendations to designers and masters for avoiding head seas parametric rolling situations.