parametric rolling

最近有一個新的概念, 就是Parametric rolling, 它會發生於大型貨櫃船之艏艉之處, 茲於此介紹

http://www.marineinsight.com/misc/mar ... lling-in-container-ships/

http://www.youtube.com/watch?v=ewqaRMGv2mE


Rolling and pitching is a part of every ship that is going out at the sea. The first thing you might think up on hearing the word 「Parametric rolling」 is that it must be a type of rolling movement occurring in ships. Rolling and Pitching is a normal movement phenomenon which occurs in all kind of ships, so what is new about this? The difference is that 「Parametric Rolling」 is a type of movement that is experienced only on Container Ships.

Causes of Parametric Rolling: The size of container ships is increasing drastically as companies are looking forward to monster ships; for e.g. Maersk』s Triple-E Vessels. The new container ships coming to the market have large bow flare and wide beam to decrease the frictional resistance which is generated when the ship fore end passes through the water, making it streamlined with the hull. As the wave crest travels along the hull, it results in flare immersion in the wave crest and the bow comes down. The stability (GM) varies as a result of pitching and rolling of the ship. The combination of buoyancy and wave excitation forces push the ship to the other side. http://www.youtube.com/watch?v=ewqaRMGv2mE (Parametric roll).