The Vibration Damping of a Ship in her Moving State

概要

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As a continuation of the authors's last investigation concerning the causes of the vibration damping of a ship, the same authors newly found that there is an additional vibration damping of a ship in her moving (ahead) state.-the damping originating from the movement of the ship's hull relative to the water. Using a circulation water tank, the authors conducted model experiments of free as well as forced vibrations, from which it was ascertained that the vibration damping enormously increases with increase in water velocity relative to the model, and, furthermore, that the results obtained from separate methods of tests, namely forced vibration test and free vibration test, fairly agree. The same results were confirmed by means of a statical hydrodynamic test, though the idea about it is rather inexact. From the results of experiments, the damping constants of a flat surface vibrating normal to water stream were deduced, from which it was possible for the authors to estimate, in speculation, the damping coefficients of an actual ship moving at various speeds. It was shown that in the case of an actual ship, the estimated theoretical damping coefficient is of the order of magnitude as the actual one, particularly in moving-ahead condition, at low speed, of the same ship.
社団法人日本船舶海洋工学会の論文
1939-03-10