Abstract

The equation of motion of the water column and the experimental method were developed by Fung (1996a). The added mass and damping of the water column were evaluated experimentally and the water column response under wave excitation were predicted numerically. Three moonpool models, each representing one special feature, have been presented. It was found, for a given frequency, that the added mass and damping were not single valued, but dependent upon the directions of the acceleration and velocity respectively of the oscillation. For a given draft the smooth moonpool of constant cross-section had the lowest added mass and, therefore, the highest peak response frequency (PRF). The damping devices lowered the PRF, which could only be raised by changing the configuration, for example, an enlarged section at the mouth. The amount and kind of damping could be realized by various physical damping devices in order to control the water column response. Generally, the response was found to shift upward due to the difference of damping between the up-stroke and the down-stroke.