静止から横移動を開始する船体の横力係数に関する検討

概要

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The lateral drag coefficient obtained by the Constant Accelerating Test(CAT) shows us an extremly large numerical value in the beginning of movement of a ship-model. This coefficient gradually decreases every second and finally converges to a steady numerical value after the ship-model has moved more than about 2 ship-lengths. The steady value is about half of a constant numerical value which has been usually applied. Accordingly at present, we can apply three kinds of the lateral drag coefficient to the estimation of tug-power, namely (1) constant value, (2) transitionally changing value and (3) steady value. But in order to estimate reasonably tug power, it is necessary to select the proper coefficient for the condition of a ship moving laterally from rest, such as approaching a birth. First, in this paper, the property of the above coefficient (2) is examined through an another type of ship-model test. Next, the effective tug-pull is considered based on the relation between results calculated using the coefficient (2) and data of actual survey at seas. The obtained results are as follows; (1)It was comfirmed that the lateral drag coefficient when ships moving laterally from rest transitionally changes depending on moved distance. (2)The mathmatical expression of the above coefficient was suggested. (3)The effective tug-pull in tug handling was about 80% of the published tug-pull.
1996-09-25