基于粘性流和势流耦合计算模型的破损船舶残存能力评估研究

The survivability of a damaged ship is one of critical criteria for ship safety assessment. The approach which is prescribed in the existing regulations for assessing damaged ship’s survivability lacks the ability of modeling the real physics during its flooding process. As a result, although a ship meets the regulation requirements, it may capsize or sink rapidly after it is damaged. To account for the complex mechanism in the flooding process, this research project proposes a numerical method, which integrates the viscous flow and potential flow theories, to solve the hydrodynamic problem of a damaged ship upon flooding. In this integration method, the dynamics of water ingress or egress through the damaged opening and sloshing inside the ship’s compartments are calculated based on the viscous flow theory, whereas the hydrodynamic forces induced by the external sea waves on the external hull surface are calculated based on the potential flow theory. The proposed method can yield high-fidelity numerical results with acceptable computational cost. Then the damaged ship’s survivability can be assessed based on its actual performance in realistic sea state. In conclusion, the newly developed high-fidelity numerical method can provide a convenient, efficient and reliable tool for assessment of damaged ship survivability. Based on the analysis of simulation result, the interactive dynamics between ship hull, external sea wave, water flooding, water sloshing and air will be clarified. The inherent mechanism attributed to the loss of damaged ship due to flooding will be revealed. The main findings in this research can provide theoretical evidence to amend existing design concept, regulation requirement and emergency measures towards the improvement of ship safety.

船舶受损后的残存能力是衡量船舶安全性的一项重要指标。现行规范中采用的船舶残存能力评估方法由于忽略了船舶破舱进水真实的物理过程，导致满足规范衡准要求的船舶在破损后迅速倾覆或沉没的事件时有发生。本项目针对破损船舶水动力问题力学机理的复杂性，提出结合粘性流理论和势流理论的方法对该问题进行求解，即基于粘性流理论求解水体进出船体及在船舱内运动问题，而船体与外部波浪相互作用问题基于势流理论求解。上述方法可以在比较经济的计算耗费下取得高保真度的计算结果，进而根据船舶在实际海况下的真实性能对其残存能力进行评估。通过本项目的研究，开发得到破损船舶运动流场高保真度数值模拟工具，为船舶残存能力评估提供方便、高效、可靠的计算手段。此外，通过分析船体、外部波浪、流过破口水体、舱内水体和空气之间的相互影响，揭示船舶受损进水而倾覆的内在机理，为提高船舶安全性而制定更加完善的设计方案、规范要求和应急措施提供技术支撑。

船舶受损后的残存能力是衡量船舶安全性的一项重要指标。在船舶残存能力评估中忽略船体与水体之间的动力学机理是导致满足规范衡准要求的船舶在破损后发生倾覆或沉没的根本原因。针对破损船舶动态行为预报精度不高以及相关力学机理认识不够的现状，本项目对破损船舶动力学建模方法及其运动行为开展研究。已完成的工作内容概述如下：（1）开发了破损船舶水动力粘性流求解器，用于破损船舶在静水中运动预报；采用一艘破损驳船的水池试验数据对开发的粘性流求解器的有效性进行了验证。（2）开发了耦合粘性流求解器和势流耐波性求解器的计算模型，用于规则波中船舶破舱进水过程模拟；通过与一艘破损客船的试验数据比较，验证了耦合计算模型的有效性。（3）提出了一种适用于波浪作用下船体大幅运动模拟的动网格策略，测试算例包括聚焦波生成和传播以及波-物相互作用数值模拟，证明了所提出的动网格策略具有较高的计算精度和效率。（4）进行了一系列数值模拟试验，包括静水中破损船舶瞬态和递进进水过程模拟、静水中破损船舶横摇衰减模拟、静水中破损舱室下沉运动模拟、规则波中破损船舶进水平衡阶段船舶运动响应模拟、规则波中破损船舶瞬态对称进水和瞬态不对称进水过程模拟；分析了舱室通风条件和环境压强对破舱进水量、舱内水运动及船体运动影响，破损舱室晃荡效应对船舶横摇固有特性的影响，波浪作用下敏感因素（舱室破损时刻、波浪参数和舱室布置）对舱室进水演变和船体动态行为影响，瞬态进水阶段船体倾覆机理，不同海况随机波对破损船舶运动影响。研究中所开发的破损船舶运动计算模型可为破损船舶动力学机理分析及其残存能力评估提供一种新的、可靠的工具。此外，研究中发现的结果可为提高船舶安全性而制定更加完善的设计方案、规范要求和应急措施提供参考依据。