波浪作用下“液舱-多浮体系统”的多重共振机理研究

During the side-by-side offloading operation between FLNG and LNG carrier, a system of liquid tanks and multiple floating bodies is formed. The system in waves is expected to undergo three types of resonances, i.e. the sloshing resonance in tanks, body motion resonance and gap resonance between adjacent floating bodies. These resonances normally correspond to different natural frequencies, so that any two of them cannot occur simultaneously in regular waves. However, in irregular waves, wave components of different frequencies may trigger the simultaneous occurrence of several resonances, leading to the multiple resonance phenomenon. The multiple resonance problem can result in the large-amplitude motion and collision of floating bodies, which endangers the safety of operation at sea. However, few studies on the multiple resonance problem have been carried out. Based on theoretical, experimental and numerical methods, this project will develop an efficient nonlinear numerical wave tank for the system of liquid tanks and multiple floating bodies. Two situations when sloshing and body motion resonances occur simultaneously, and when sloshing and gap resonances occur simultaneously are discussed. The project aims to investigate hydrodynamic characteristics of these two types of multiple resonances, and deepen the understanding of the interaction mechanism of the sloshing and body motion. This study will be meaningful to promote the deployment of FLNG in China.

FLNG与LNG船进行并靠卸载作业时，形成“液舱-多浮体系统”。在波浪作用下，该系统至少会面临三种共振响应形式，即液舱晃荡共振、浮体运动共振和浮体间水体共振。由于这三种响应分别对应着不同的固有频率，在规则波中很难出现某两种共振同时发生的情况。然而在不规则波作用下，不同频率的波浪成分很可能将系统的多种共振形式同时激发出来，形成多重共振现象。多重共振容易引发浮体大幅运动和浮体间碰撞，严重威胁海上作业安全。而目前关于“液舱-多浮体系统”多重共振问题的研究还非常缺乏。本项目拟结合理论分析、模型试验和数值模拟方法，为“液舱-多浮体系统”建立高效的非线性数值波浪水池。研究波浪作用下液舱晃荡和浮体运动同时发生共振、以及液舱晃荡和浮体间水体同时共振的情况，揭示这两种多重共振问题的发生条件和水动力特性，深入认识波浪与“液舱-多浮体系统”发生耦合作用的复杂机理。对加快我国布置FLNG的步伐有重要意义。

本项目以FLNG与LNG船并靠卸载作业时形成的“液舱-多浮体系统”为背景，围绕波浪作用下液舱浮体系统的多重共振响应问题，发展出“液舱-多浮体系统”的水动力解耦算法，为非线性波浪中“液舱-多浮体系统”水动力学问题建立了高效的数值波浪水池预报方法。基于数值波浪水池，研究了强非线性波浪的生成和演化规律及其对浮体结构作用的非线性水动力特性和翻卷砰击机理。通过数值模拟和模型试验的协同作业，明确了波浪中“液舱晃荡共振”、“多浮体间水体共振”和“液舱-浮体系统共振”等共振现象的发生条件，研究了共振发生时系统的水动力特性，深入揭示了非线性波浪、液舱晃荡和浮体运动之间的耦合作用机理。其中，针对液舱晃荡共振问题，建立了基于连续小波变换的非线性共振分析方法，研发了液舱晃荡的试验分析技术，发现了二阶非线性共振现象，提出了液舱共振晃荡的抑制机理；针对浮体间水体共振问题，研究了波浪中双浮体间水体共振的非线性特性和机理，分析了波浪中双浮体间水体共振的粘性效应；针对液舱-浮体系统共振问题，利用数值波浪水池研究了液舱浮体系统的耦合作用特性和共振机理。依托本项目，在国内外海洋工程领域的知名期刊上，发表论文19篇，其中SCI收录15篇，EI（非SCI部分）收录3篇；完成相关软件著作权2项，另获授权专利11项；参加学术会议14次，包括本专业国际会议7次、国内会议7次，并发表会议论文16篇（其中EI收录3篇）；培养研究生9人。