Free Rolling Test at Forward Speed

Abstract

To investigate the effects of forward speed on the rolling motion of ships, a number of free rolling tests with five models were carried out in which both the breadth of the bilge keels and the natural rolling period of models were varied systematically. The results are outlined as follows; The linearized non-dimensional damping coefficient κ generally increases with forward speed and has a slight hump-hollow undulation at F_n≒0.2, which seems due to the wave-making roll damping. The part of the coefficient κ which is ascribable due to the effect of the bilge keels remains nearly constant at forward speed. A considerable change in the natural roll period appears in the high speed range.