Dynamically Induced Roll in Head Seas
CDR Clippinger, Dr. Garcia, and Dr. Taylor, from the engineering department, presented a paper on ship motions in waves at the November 2012 national conference of the Society of Naval Architects and Marine Engineers in Providence, Rhode Island. The paper was entitled “Dynamically Induced Roll in Head Seas.”
The research revealed that ships, even when the course of the ship is directly into oncoming waves (head seas), will roll – rock from side to side – sometimes violently. It has long been recognized that periodic variations in the stability of a ship result from the passage of these “head seas” and the associated variation in the shape of the ship at the sea surface, which causes rolling. But, this research identified a second contributor to roll motions driven by the mathematically based dynamic coupling of ship motions with the ship’s weight distribution. Computations were performed for both a commercial ship and a Coast Guard ice-breaking ship.
The paper identifies techniques for both naval architects and ship operators to reduce or eliminate roll induced by characteristics of hull shape and the distribution of cargo on board.