我国南海海啸波爬高及其共振机理研究

With the frequent occurrences of giant tsunami disasters in recent years, early warning of tsunami and disaster prevention and mitigation have become a hot issue of international concern. Since the destructions of coastal area in the tsunami events are caused by the wave runup, studies on the runup of tsunami and the disaster mechanism have become an essential project. Great effort has been made on the study of solitary wave runup in the last decades. Many useful results have been obtained by both analytical methods and numerical methods, as well as physical experiments. In fact, the bulk of the tsunami is very poorly represented by solitary waves and the front of the tsunami hardly ever develops into solitary waves. .In this project, numerical simulations and physical experiments are combined to study the generation, propagation and runup of tsunamis in South China Sea. The tsunami waveforms near the coastal area will be calculated numerically with the fully nonlinear and highly dispersive Boussinesq wave model. Based on the reasonable submarine earthquake model and the actual topography of South China Sea, the waveforms will be relevant to the real tsunami waves near the shore. Taking these waveforms as the incoming wave boundary conditions, the tsunami experimental method in the wave flume will be developed. Real tsunami waves including N-waves, dispersive wave trains and undular bores will be obtained in the wave flume..The physical model experiments will be carried out to investigate the resonance phenomenon of tsunami waves on special topography, such as sloping beaches and offshore submerged dikes. The influence of the special topography and offshore structures to the tsunami resonance will be evaluated quantitatively. Based on the actual topopraphy and structures in the coastal area of South China Sea, the runup of tsunami, wave evolvement and transformation between kinetic energy and potential energy of wave motion during the runup and rundown processes, as well as local runup amplification by the resonance of tsunami waves will be studied experimentally. These researches will provide necessary benchmark to the numerical simulation of tsunamis. Meanwhile, the results will be helpful to establish the warning system of tsunami and provide scientific basis for the development of disaster prevention and mitigation strategies.

海啸在近岸爬高及其成灾机理研究是一项基础性研究课题，物理模型实验是研究该问题的重要手段，目前实验研究的来波条件多为孤立波，事实上传播到近岸的海啸波很少能与孤立波在波形上匹配。本项目采用数值模拟与水槽实验相结合的方法，基于我国南海实际地形，采用完全非线性高阶色散性Boussinesq水波模型，模拟海啸波传播到近岸的实际波形，以此作为来波边界条件，建立海啸波水槽造波方法，在实验水槽中模拟N波、色散波列和波状水跃等形式的近岸海啸波。通过模型实验，研究海啸波传播到斜坡和离岸式潜堤等特殊地形上发生的共振响应，定量评价特殊海底地形和工程结构对海啸共振的影响。结合我国南海典型海岸地形和防护结构，研究海啸波的爬高、波形演化、能量转化和共振规律，为发展海啸数值模型提供必需的基准实验数据。研究成果可用于分析海啸成灾的力学机理，并为海啸预警系统的建立和防灾减灾策略的制定提供科学依据。

本项目基于我国南海实际地形，针对马尼拉海沟潜在的地震海啸风险，采用完全非线性高阶色散的水波模型，系统地模拟海啸生成和传播过程，获得近岸海啸波形，建立我国南海典型海啸波基本形态图谱。基于典型海啸波模拟结果，建立造波板运动规律与目标波形之间的关系，实现近岸海啸波的实验模拟。通过物理模型实验，研究海啸波近岸爬高规律，揭示海啸波在特殊地形上的共振响应机理。.(1) 基于完全非线性高阶色散性Boussinesq波浪模型模拟近岸海啸波形。（按项目计划书执行）.基于完全非线性高阶色散性平面一维Boussinesq 波浪模型，将海底地震概化模型作为反映震源运动过程的底面动边界加入海啸波传播计算模型，建立起完整的海啸生成、传播和爬高的数值模型。针对我国南海的地形地貌和马尼拉海沟断裂带的位置和走向，进行了系统的海啸生成和传播的平面一维数值模拟。分析了海啸生成的瞬态响应过程以及海啸波传播过程中的色散特性和非线性，揭示了海底地形对海啸波演变的影响，建立了考虑特定海岸地形地貌影响的近岸海啸波形图谱。.(2) 建立海啸波室内模拟方法。（按项目计划书执行）.将Goring 造波方法应用到海啸波造波中，在实验水槽中获得孤立波、双孤立波、N 波和波状水跃等形式的海啸波，实现了海啸波的水槽造波和同步测量技术。.(3) 研究海啸波在特殊地形上的共振机理。（按项目计划书执行）.以不同的来波条件和地形因素在波浪水槽中进行分组实验。通过改变入射波的波参数和斜坡坡度，采用沿水槽分布的浪高仪测量海啸波在斜坡上的爬高，分析不同形式和海啸波的爬高放大系数，以最大爬高值作为考察海啸波发生共振的指标。同时利用高速激光粒子测速系统(PIV)测量波浪爬高时水舌附近流场的速度分布，并拍摄波形的演化过程。.(4) 研究海啸波在我国南海典型海岸上的爬高和可能发生的共振响应。（按项目计划书执行，另新增部分研究内容）.基于我国南海真实的海底地形，归纳若干组复合海底地形工况，在水槽中进行分组实验，测量海啸波在几种地形上的爬高值，分析地形对海啸波爬高共振的影响。另外，结合物理模型实验结果，课题新增了海啸波在复合斜坡地形上共振的解析和数值研究。