基于操纵-耐波统一理论的最小推进功率综合评估

Comprehensive Assessment of Minimum Propulsion Power Based on Manoeuvring-Seakeeping Unified Theory

为了满足EEDI的要求而降低装机功率,可能导致船舶在恶劣海况中失去操纵性,不能安全航行。在IMO发布的2021最小推进功率导则中对装机功率作了强制性要求,但未明确与操纵性尤其是航向稳定性相关的要求,且基于简化平衡方程的第二层次评估无法考虑波浪漂移力的影响。论文基于实海域操纵-耐波统一理论对KVLCC2航向保持运动进行模拟,开展最小推进功率的第三层次综合评估,并将其与第一、第二层次评估比较,分析最小前进速度、最大偏航角和浪向范围的影响。波浪横向漂移力与转首漂移力矩作用的考虑与否可使偏航角预报的偏差达80%以上,开展综合评估需完整考虑波浪漂移力和操舵动态过程的影响。建议在现行导则中增设最大偏航角10°~15°的要求,能更可靠地保证恶劣海况中船舶的安全操纵性能。

Simply reducing installed power of ships to achieve required EEDI may lead to the loss of maneuverability in adverse conditions and the inability to maintain safe navigation.The 2021 guidelines for determining minimum propulsion power issued by IMO impose mandatory requirements on the installed power in two assessment levels,but relevant requirements for maneuverability,especially the course stability,have not yet been specified,and the impacts of wave drift force and moment are not considered in the simplified equilibrium equation of the level-2 assessment.In this paper,a series of time-domain simulation of course-keeping maneuvering for KVLCC2 in adverse conditions was carried out based on the manoeuvring-seakeeping unified theory in actual seas.Then,the level-3 comprehensive assessment of minimum propulsion power was carried out and compared with the level-1 and level-2 assessments,and the influences of minimum forward speed,maximum yaw angle and wave direction range were discussed.Whether the action of wave lateral drift force and yaw moment is considered or not can make the deviation of yaw angle prediction reach more than 80%,so effects of wave drift force and steering dynamic process should be fully considered in the comprehensive assessment.It is suggested that the maximum yaw angle of 10~15 degrees should be supplemented into the guidelines so that the minimum propulsion power assessment can more reasonably ensure the maneuverability and safety of ships in adverse conditions.