On the Maximum Transverse Inclination of a Ship during the Stage of Flooding

Abstract

The motion of a ship during the flooding stage is obtained by the numerical integration of the equation of her transverse motion, with the assumption that the level of the flooding water is always horizontal, its quantity increasing with time. The typical passenger ship of 20, 000 tons with the met. ht. of 0.44 m. is adopted and the length of the flooded compartment is taken to be one fifth amidship of the ship's length, and the area of the damage hole is chosen at the side, its value being changed variousely. Main results obtained are as follows : (1) Max. heel changes with the initial conditions, that conditions being that the ship is initially at rest and inclined at θ0. The value occurs at nearly θ0=1°5°.(2) Max. heel changes with the area of the damage hole. The greatest value occurs at nearly 10 m2, and if the area is greater than 40 m2, the max. heel is very small.(3) The greatest heel obtained is nearly twice of the value which can be calculated by the statical consideration, i.e. by assuming the water quantity being constant, if the resistance to the motion is neglected, and is 1.4 times, if the resistance is taken into account.(4) For the larger met. ht, if the damage hole is very small, say less than 5m2, the oscillatory motion of increasing amplitude gives rise to, in the early stage of flooding, resulting to the very great heel. But in such a case, the flooding water may act so as to damp that motion, the assumed condition of horizontal level not being fulfilled, but the actual procedure should be studied experimentally. If such cases be put aside, the max. heel for the larger met. ht, is generally less than that for smaller met. ht.(5) From the above investigations, it is concluded that the max. heel statically obtained, as is generally adopted, does not indicate the real one, and that such a problem should be treated dynamically.