Rolling of a Ship

Rolling of a Ship 

rocking of a floating vessel caused by waves or other external forces.

The three types of rolling are normal rolling (inclination from port to starboard), pitching (inclination from bow to stern), and heaving (translational displacement in the vertical direction). Simultaneous pitching and heaving in the same or opposite direction as the waves is called fore-and-aft rolling; simultaneous rolling and heaving with lateral choppiness is called transverse rolling. All types of rolling usually occur simultaneously. Rolling is characterized by amplitude, period (frequency), and phase shift of the oscillations relative to the external force. Resonance may be observed during rolling.

Rolling causes a reduction in the velocity of the ship, negatively affects the human organism (seasickness), and adversely affects the working of machinery and instruments and the utilization of military equipment. During intense rolling, the ship may capsize because of external loads not dangerous in the absence of rolling. Moderation in rolling is one of the most important features of the seaworthiness of a ship. The longer the period and the smaller the amplitude of rolling, the better the seaworthiness. Ship stabilizers are installed to control rolling. The fundamentals of the general theory of rolling were developed by Academician A. N. Krylov.

REFERENCES

Semenov-Tian-Shanskii, V. V., S. N. Blagoveshchenskii, and A. N. Kholodilin. Kachka korablia. Leningrad, 1969.
Borodai, I. K., and Iu. A. Netsvetaev. Kachka sudov na morskom volnenii. [Leningrad, 1969.]

L. N. STRELIAEV