バウスラスター性能に及ぼす前進速度影響の理論的推定

抄録

Bow thruster equipped with in a ship is often used in order to improve manoeuvrability of a ship which is moving in restricted water or is berthing. When a ship is stopping or moving in low speed, bow thruster is one of the effective devices. But it is well known that the force and moment produced by thrusters decrease as forward speed of ship increase. Therefore it is very difficult to grasp the effect of these thrusters on ship manoeuvrability when ship is moving with forward speed. However, it is necessary to understand the performance of thruster from a view point of marine safety because thrusters are often used in overcrowded sea route or narrow water way. As to these problems, one of the authors has already proposed prediction method of thruster performance in the previous paper. In this prediction method, ship is substituted with a rectangular wing. Furthermore, the authors have also proposed the prediction method which includes effect of ship breadth roughly. However, those prediction methods represent only tendency of deterioration of thruster performance. In this paper, we proposed new model of entrainment function which have much influence on accuracy of prediction of jet path spouting from thruster. From the results of numerical calculations using the new model of entrainment function, it is shown that predicted jet path gives good agreement with experimental result. Furthermore we also proposed prediction method of hydrodynamic interaction forces between ship hull and the jet including effect of three-dimensional hull form, we carried out prediction of the hydrodynamic interaction forces and it is shown that the prediction method expresses the transition of lateral force and yawing moment as a function of forward speed of ship with high accuracy.