The lateral damping and added mass of a horizontally oscillating shipmodel 1 2

Abstract

For a practical range of circular frequencies forced sway and yaw tests were carried out, to obtain the values of mass and damping and their linear cross-coupling effects.

Cross-coupling damping effects are considerable, but the apparent mass centre of gravity appeared to be located close to the model’s centre of gravity. In general the results agree with those of Paulling [1]. The influence of the rudder and the propeller in the low frequency range is shown clearly, except the influence on the moment of inertia coefficients. The results of the combined sway and yaw tests in general agree with the comparable pure motion results. The differences found will partly be caused by higher order cross-coupling effects, partly by the possible error of the test data. It seems that even for higher frequencies linear equations of motion may be applied.

As a secondary result the stability indices could be determined from the obtained values of the various coefficients. For a restricted frequency range negative stability was found. This result may be related to the critical state of the wave pattern generated by the oscillating model.