考虑波流相互作用的畸形波水动力学特性及其对海洋结构物载荷的预报方法研究

Wave-current interaction is one of the important physical mechanisms of the freak wave phenomenon. The plunging and breaking processes which are strongly nonlinear are often observed when freak waves propagate in the ocean. In this study the influence of wave-current interaction on the hydrodynamic property of freak wave and its load on ocean structure is studied thoroughly. Moreover, the effect of flow viscosity is taken into account. This research contains two parts, namely hydrodynamic characteristic of freak wave and wave induced load on ocean structures by means of experiment and numerical simulation. The first part of study will focus on formation and propagation as well as breaking of the freak wave on current. The experiment will be conducted in the circulating water channel (CWC) of SJTU (the flow field is measured by Particle Image Velocity (PIV), water elevation is measured by wave gauges, and the pressure is measured by pressure sensors). Meanwhile a newly independently developed numerical flume which is based on the large eddy simulation (LES) and the finite volume method (FVM) is applied to simulate freak wave. The concentrating position, evolution of water surface and flow field of freak wave on current with various velocities will be studied. Furthermore the limit and the process of freak wave breaking and the variety law of the energy dissipation will be discussed. The physical mechanism of the freak on current will be further revealed, and the corresponding theories will be established accordingly. The second part of this study will focus on the hydrodynamic property of freak wave interacting with ocean structure and the energy dissipation of freak wave after passing by ocean structures. In certain scenario, the impact load of freak wave imposes on ocean structures can be very dangerous. So in order to estimate the load caused by freak wave, thorough investigations on the phenomenon and the mathematic model will be performed. Finally, an efficient and accurate prediction method will be proposed based on the experimental results and numerical simulation.

波流相互作用是畸形波形成的重要原因之一，畸形波形成后，在传播过程中，往往会伴有翻卷、破碎等强非线性现象，考虑上述因素，本研究专门针对有流作用下的畸形波及其对结构物的载荷进行深入研究，并同时考虑水流的粘性效应影响。拟开展以下两方面的试验和数值模拟研究： 一、在试验水槽和自主开发的数值水池（基于有限体积法的大涡模拟）中采用波浪聚焦的方法生成畸形波，研究不同流速作用下畸形波的聚焦位置、波高、流场结构的变化以及畸形波的破碎过程及其能量耗散规律，并进一步揭示流作用下畸形波的形成机理并形成相应理论。二、在对畸形波的特性有深入了解的基础上，研究流作用下的畸形波与海洋结构物相互作用时的水动力学特性，以及畸形波在遭遇结构物后的能量耗散规律等。在此基础上，针对工程中最关注的畸形波对海洋结构物的载荷问题进行深入研究，在结合大量的试验数据和数值模拟结果的基础上，探索载荷的预报公式，并研发精细、高效的数值预报软件。

波流相互作用是畸形波形成的重要原因之一，畸形波形成后，在传播过程中，往往会伴有翻卷、破碎等强非线性现象，考虑上述因素， 本研究专门针对有流作用下的畸形波及其对结构物的载荷进行深入研究，并同时考虑水流的粘性效应影响。拟开展以下试验和数值模拟研究：.本项目自主研发了高精度的大涡模拟数值模拟软件，该软件在空间离散采用四阶紧致格式，时间推进采用四阶龙格库塔法，湍流的求解采用Smagorinsky亚格子应力模型，采用浸没边界法实现对结构物的模拟。基于该软件实现了对各种非线性波浪及其与结构物相互作用的高精度大涡模拟。首次采用ITTC推荐的不确定度分析方法对畸形波数值模拟的数值误差和不确定度进行定量计算。此外，通过不确定度分析和流场对比，证明了本软件与商业软件Fluent相比的优越性。.在试验水槽和数值模型中采用波浪聚焦的方法生成畸形波，研究不同流速作用下畸形波的形成、演化和破碎。研究流作用下畸形波的聚焦位置、波面、流场结构的变化规律，并进一步揭示流作用下畸形波的形成机理。在对畸形波的特性有深入了解的基础上，结合PIV技术研究流作用下的畸形波与海洋结构物相互作用时的流场和水动力学特性。