不规则波浪中的船舶操纵性数值预报研究

Numerical prediction of ship maneuverability in irregular waves is studied in this project. The motion equation of the ship maneuvering in irregular waves is proposed by adding the irregular wave drift forces into the modular type maneuvering model. In order to increase the accuracy of the numerical simulation, the "quasi-steady" and "direct time-domain calculation" methods are applied to deal with the coupling between the irregular wave drifting forces and the ship's maneuvering motion, and the influences of the longitudinal velocity, transverse velocity and yaw rate of the ship are considered simultaneously in the calculation of the wave drift forces. Numerical simulations of the typical maneuvering tests in short-crested waves are carried out for the ships which are commonly used in the international maneuvering study. Based on the numerical results, the changes of the maneuvering performance parameters in relation to the characteristic parameters of the irregular waves are summarized. The simulated ship maneuvering motions in irregular waves are compared with the ones under calm water and regular waves. The comprehensive influences of the irregular waves on the ship maneuverability are also discussed. The mathematical model of the main engine is further coupled into the proposed numerical model of the ship maneuvering. The minimum power requirement of the ship is studied, from the viewpoint of maneuvering safety, by simulating the typical maneuvering motion of ships with different main engine powers in the adverse sea conditions. The successful implementation of this project is of some value to improve the maneuverability of ships during voyaging at rough sea.

本项目拟开展不规则波中的船舶操纵性数值预报研究。通过将不规则波浪漂移力作为外力计入分离型船舶操纵运动模型，建立不规则波中的船舶操纵运动方程，采用“准稳态”和“时域直接计算”两种途径处理不规则波漂移力与船舶操纵运动的耦合，并在波浪漂移力计算中同时计及船舶纵向速度、横向速度和转首角速度，以确定更为准确的不规则波中船舶操纵运动数值模拟方法。选择国际上广泛用于操纵性研究的标准船型，数值模拟其在短峰不规则波中的典型操纵运动，获得各种操纵性能指标随不规则波特征参数及船舶初始航速的变化规律，并将不规则波中的船舶操纵运动与静水及规则波中的结果进行比较，深入探讨不规则波对船舶操纵运动的影响机理。在操纵运动数学模型中进一步增加主机控制模型，通过模拟各种海况下不同主机功率船舶的典型操纵运动，从操纵安全角度对船舶的最小主机功率需求进行研究。本项目的成功开展，可为切实提高复杂海况中的船舶操纵性能提供参考依据。

近年来，波浪中的船舶操纵性受到了船舶工程界的普遍关注。本项目对不规则波浪中的船舶操纵性数值预报方法进行了系统研究，将不规则波浪漂移力作为外力计入分离型船舶操纵运动模型，建立了针对船舶在不规则波中操纵运动的数值预报程序。通过系统地验证并拓展已有的势流理论及相关计算方法，保证了规则波和不规则波漂移力计算的准确性。对比了“时域直接计算”和“准稳态计算”在处理在波漂移力与船舶操纵运动的耦合分析时的效果，证明了“准稳态”假定的有效性。通过比较长峰、短峰不规则波以及波浪平均漂移力和低频慢漂力的效果，证明了计及长峰不规则波平均漂移力的操纵运动方程是一种能够较好地评判船舶在波浪中的操纵性能的数学模型。开展了不规则波对船舶操纵性能的综合影响研究，证明了不规则波的有义波高对船舶操纵轨迹的影响较为明显，20%的有义波高增幅引起的漂移距离的增量达到40%以上；波浪平均周期的变化对漂移距离的影响则相对温和。通过在操纵运动模拟中进一步考虑主机功率影响，证明了主机功率的受限将造成船舶在波浪中回转能力的显著下降，五级海况下考虑主机功率影响后船舶的平均转首角速度下降了约50%。本项目研究所建立的数学模型和开发的数值预报程序，能够为船舶工程中预测真实波浪环境下的船舶操纵性能提供有利的工具。项目研究所得到的数据和相关结论，对于提高船舶在实海况下的航行安全性也有重要的参考价值。