Page 21: of Maritime Reporter Magazine (November 2004)

Naval Architecture & Marine Engineering length of the sea conditions through which it is passing; and its speed must bear a certain relationship to both the wavelength and the vessel's natural rolling frequency.

The 1998 incident and its severe cargo loss warranted a full investigation, the results of which opened the maritime industry's eyes to a long-standing prob- lem, the impact of which it had not yet fully appreciated. This investigation, which included model tests and numeri- cal simulations, determined that hulls with fine, underwater bodies coupled with wide, flat sterns and pronounced bow flare - typical of modern container- ships - may be susceptible to parametric roll.

ABS began its own investigations into the causes and remedies for parametric roll. The two-year project has involved theoretical analyses and numerical sim- ulations, and included collaboration with Prof. J. Randolph Paulling, who in the 1970s first observed the paramet- ric roll phenomenon in model tests. "Shipowners would often approach me at conferences with nervous ques-

An ABS research project deflates the mys- tique surrounding parametric roll, a rare but dangerous phenomenon particularly threatening to containerships. tions about parametric roll, asking why and how it happens." says Vadim

Belenky, the engineer leading ABS' investigations into parametric roll. "Over time, I came to see that there is a kind of mystique and fear about this phenomenon," A ship motions specialist and former professor at the Kaliningrad

University of Technology in Russia,

Belenky is still an educator at heart and has dedicated himself to understanding and explaining the phenomenon. "The message I want to communicate to the industry is that there is no mystique to parametric roll. We at ABS understand the phenomenon very well and are tak- ing actions to help keep our clients safe from it."

The Problem

Parametric roll is a phenomenon that occurs in head or following seas, when a ship is traveling more or less perpendic- ularly to the wave front. The phenome- non was first recognized almost 50 years ago but, in the past, it was seen as affect- ing only smaller ships of poor stability in following seas. The development of

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