Improvement of Prediction of Maneuvering Performance in Shallow Water

准确预测船舶的操纵运动是提高船舶航行安全的基本要求。对于船舶以中等前进速度航行的情况，深水机动性能数值模拟的有效性已经得到充分的证实。相反，需要更多的努力来阐明与浅水机动运动有关的水动力方面，并验证用于描述浅水航行船舶的水动力的数学模型。在目前的研究中，主要侧重于以下两个项目；(1)建立了作用于低速浅水船舶的水动力数学模型。特别是，数学模型的发展，即使船舶有过大的摇摆速度和/或偏航角速度。(2)螺旋桨反转船舶停止机动数值模拟的有效性检验。关于第一项，进行了大量的自保模型试验，然后提出了一个数学模型。对于第二项，将停止机动的数值模拟结果与自由运行模型试验结果进行了比较。结果表明，通过数值模拟可以较准确地预测停车动作的宏观质量，即轨道距离、车头距离、侧面距离、停车时间和停车角度。

Accurate prediction of manoeuvering motions is essential requirement for enhancing the navigation safety of ships. The usefulness of numerical simulation of maneuvering performance in deep water has been fully established for the case where a ship travels at a moderate forward speed. On the contrary, more efforts are necessary to clarify the hydrodynamic aspects relating to maneuvering motions in shallow water and to validate the mathematical model developed to describe the hydrodynamic forces on a ship traveling in shallow water.In the present research, main emphasis is placed on the following two items ;(1) development of mathematical models for hydro- dynamic forces acting on a ship traveling at a low speed and in shallow water. Especially, development of mathematical models useful even when a ship has excessive sway velocity and/or yaw angular velocity.(2) Examination of usefulness of numerical simulation of stopping maneuvers of ships with reverse rotation of propellers.Concerning the first item, an extensive amount of captive model tests were carried out, and then a mathematical model was proposed. Regarding the second item, results of numerical simulation of stopping maneuvers were compared with the results of free-running model tests. As a result, it was confirmed that the macroscopic qualities of stopping maneuvers, i. e. track reach, head reach, side reach, stopping time and stopping angle could be predicted by numerical simulations with enough accuracy for practical purpose.