Abstract The ship manoeuvrability in actual seas with both wind and waves, especially in adverse weather conditions, for a full-scale tanker with different maximum available power of the engine is studied. It is directly evaluated based on the result of a free-running model test (FRMT) under a course-keeping manoeuvre in long-crested and short-crested irregular waves of Beaufort scale force (BF) 7–10. The FRMT combines rudder effectiveness and speed correction considering the operational limit of an engine, and a wind load simulator, both of which were previously proposed by the authors. Therefore, not only the effect of waves but also effect of wind, rudder effectiveness of the full-scale ship, and the engine limit for continuous operation are considered in the FRMT. To validate the reliability of the direct evaluation method in FRMT and the measured data in irregular waves of large amplitude, the time-averaged manoeuvring motion of the FRMT at BF 9 is compared with ship manoeuvring motion under steady equilibrium conditions estimated using numerical simulation based on a modular mathematical model. The wave drift forces and moment in the simulation are determined on the basis of the results of the captive model test in regular waves, which is carried out using the same tanker model before the FRMT, so that we can eliminate the estimation errors in the manoeuvring motion caused by the imprecision in the wave drift forces as much as possible. The comparison shows the FRMT results acceptably agree with the simulation results, although a discrepancy is observed in the rudder angle in beam seas for the tanker with a low engine output. Further, FRMT data themselves show that full-scale rudder effectiveness, operational limit of an engine, and the engine with lower power cause the ship speed to decrease and the drift angle and the rudder angle to increase in head, bow, or beam seas because of the difference in the propeller rotational speed in each model control condition. In addition, it was clarified that operational limit of an engine also affects the significant single amplitudes of the fluctuating components of them and the oscillatory ship motion. Next, the authors assess the manoeuvring limit in adverse weather by comparing the FRMT data of the time-averaged values of the longitudinal ship speed, as well as the drift and rudder angles in short-crested irregular waves at BF 7–10 with their thresholds. The assessment clarifies that the tanker becomes unmanoeuvrable at BF 9–10 and in head, bow, or beam seas owing to a lack of sufficient advancing speed. However, the limit is not attributable to the drift or rudder angle, although the lower-power engine worsens the course-keeping ability owing to the decrease in the ship speed and the increase in the drift and rudder angles. Furthermore, the tanker is manoeuvrable in any wind and waves directions at BF 8, which is defined as adverse weather conditions for this subject ship in the interim guideline (IMO, 2013). It indicates that the tanker has sufficient margin of the engine power to keep manoeuvrability in adverse weather conditions. In summary, these findings reflect the possibility that FRMT can replace numerical simulation as a direct evaluation method of full-scale ship manoeuvring motion and limits in adverse weather.

中文翻译：

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使用自由航行模型试验估计恶劣天气下全尺寸船舶操纵性

摘要 研究了具有不同发动机最大可用功率的全尺寸油轮在风浪并存的实际海域，特别是在恶劣天气条件下的船舶操纵性。它是根据在波弗特规模力 (BF) 7-10 的长波峰和短波峰不规则波中的航向机动下的自由运行模型测试 (FRMT) 的结果直接评估的。FRMT 结合了考虑发动机运行极限的舵效和速度修正，以及风载荷模拟器，这两者都是作者先前提出的。因此，FRMT 不仅考虑了波浪的影响，还考虑了风的影响、全尺寸船舶的舵效以及连续运行的发动机限制。为验证FRMT直接评估方法和大振幅不规则波浪实测数据的可靠性，将FRMT在BF 9的时间平均操纵运动与基于数值模拟估计的稳态平衡条件下的船舶操纵运动进行比较。模块化数学模型。模拟中的波浪漂移力和力矩是在规则波浪俘获模型试验结果的基础上确定的，在FRMT之前使用相同的油轮模型进行，这样我们就可以消除操纵中的估计误差尽可能由波浪漂移力的不精确引起的运动。比较表明 FRMT 结果与模拟结果一致，尽管观察到发动机功率较低的油轮在横海中的舵角存在差异。此外，FRMT 数据本身表明，全尺寸舵效、发动机的操作限制和较低功率的发动机会导致船速降低，并且在头海、船首或横海中漂移角和舵角增加，因为每个模型控制条件下螺旋桨转速的差异。此外，明确了发动机的运行极限也会影响其波动分量的显着单幅幅度和船舶的振荡运动。接下来，作者通过比较纵向船速时间平均值的 FRMT 数据来评估恶劣天气下的操纵极限，以及 BF 7-10 处的短波峰不规则波浪的漂移和舵角及其阈值。评估表明，由于缺乏足够的前进速度，油轮在 BF 9-10 以及在头海、船首或横海中变得无法操纵。然而，该限制并不归因于漂移或舵角，尽管由于船速的降低和漂移和舵角的增加，低功率发动机使航向保持能力变差。此外，该油轮可在 BF 8 的任何风向和波浪方向上机动，这在临时指南中被定义为该主题船舶的不利天气条件（IMO，2013）。这表明油轮有足够的发动机功率余量来保持在恶劣天气条件下的机动性。总之，