分层流晃荡界面波间相互作用及与防晃隔板耦合机制的研究

Density-stratified fluids sloshing phenomena in moving containers filled with crude oil including water or liquefied natural gas belong to typical multi-interfacial fluids flow and are more complex fluid-solid coupling problems, which are one of a hot and leading edge topics in ocean engineering and have attracted widespread concerns. The large amplitude fluctuation of free surface wave and internal interfacial wave generated in violent density-stratified fluids sloshing not only degrades the performance of the topside process vessel but also seriously deteriorates or destroys the oil-water-gas separation efficiency due to additional turbulence and inter-phase mixing, which also leads to a loss of the level control.. The law of internal interfacial wave generation and propagation in closed containers fully filled two-layer liquids has been studied extensively, the interactions between free surface wave and internal interfacial wave are therefore hardly considered in stratified fluids sloshing. The effects of all kinds of parameters such as frequency, density ratio and depth ratio between two-layer fluids on stratified fluids sloshing waves will be investigated by conducting a series of physical model experiments and numerical simulations. This proposal aims to reveal the nonlinear interaction law between free surface wave and internal interfacial wave and their coupling mechanism with anti-sloshing baffle. The slamming loads of free surface wave and internal interfacial wave, their passive damping mechanism by using the baffles and effects of turbulence intensity on interface mixing between two-layer fluids will be studied and clarified. In this research, a breakthrough will be made on revealing the nonlinear interaction mechanism between free surface wave and internal interfacial wave, particularly their energy exchange and amplitude-frequency transformation characteristics, which will offer directly reference value for more extensive water wave dynamics problems. Also, this study will be more applicable for layout design of topside processing vessels on offshore production platform.

原油或液化天然气在储运中因密度差异导致的分层流晃荡属于典型的多界面流动和更为复杂的流固耦合问题，也是海洋工程的热点前沿课题。剧烈分层流晃荡过程中所生成表面波与内界面波的大幅度运动不仅会影响油气处理平台的操作性能，还会严重干扰甚至破坏正常的油水气分离进程并引发液位控制困难。. 以往分层流晃荡的研究主要关注两层液体充满密闭容器时，内界面波的生成传播规律，很少考虑表面波与内界面波的相互作用。本项目将通过模型实验与数值模拟研究各种参变量对分层流晃荡波的影响，特别是表面波与内界面波之间的非线性相互作用规律及其与防晃隔板的耦合作用机制，阐明内界面波与表面波的砰击荷载特性、被动抑制机理及紊动强度对两层流体界面混合的影响规律。研究工作将在阐明内界面波与表面波演化过程中二者之间的能量交换机制和幅频转换特性上取得突破，将对更广泛的水波动力学问题和优化油气处理平台布局具有直接的参考价值。

分层流晃荡属于典型的多界面流动，也是更为复杂的流固耦合问题，而非线性界面运动机理及流固耦合研究一直是服务海洋工程结构和装备研发不可或缺的基础性工作。以物模试验为主结合数值模拟方法对考虑自由面影响的分层流晃荡过程中界面波间的能量交换与幅频转换机制、防晃隔板或液舱底部结构物对分层流晃荡界面波的抑制机理进行了系统深入的研究。提出了一种同步追踪两个界面波的改进流体体积法，并结合模拟任意形状结构物的虚拟边界力法，自主开发了三维分层流晃荡数值模型，解决了现有理论分析中不能解决的非线性问题，并且能够精准的模拟上层以及下层液面破碎的物理现象。基于六自由度运动模拟平台发展了利用超声波传感器和图像处理技术的多界面波同步非接触式试验测试方法。分别开展了不同参数激励下的分层流晃荡物模试验研究以及防晃隔板或底部正弦结构物对分层流晃荡影响规律的研究。基于试验数据校验了数值模型并利用验证的数值模型开展了一系列数值模拟。结合试验数据和模拟结果阐明了分层流晃荡过程中内界面波和自由表面波之间的能量交换机制和幅频转换特性，揭示了界面波间的非线性相互作用机理，明确了分层流晃荡内界面波和自由表面波与防晃隔板或底部结构物之间的非线性作用机制，揭示了防晃隔板抑制分层流晃荡界面波的作用机理。本项目中建立的三维数值模型可应用于任意耦合自由度激励下的分层流晃荡载荷预测及防晃优化设计，不仅为解决油气储运、油水分离等问题提供科学支撑，而且为深入探索波-波相互作用等水波动力学问题提供了有力工具。