【作者】 郑坤；

【导师】 孙昭晨；

【作者基本信息】 大连理工大学 ， 港口、海岸及近海工程， 2009， 博士

【摘要】 随着人类对海洋资源的不断开发,海岸和近海工程建筑物的安全问题已成为研究的热点,特别是波浪对海工建筑物的的冲击作用问题。在波浪冲击过程中,当波峰刚接触到建筑物底面时会产生历时很短但强度极大的冲击压力,这种极强的冲击荷载会引起建筑物上部结构的失稳或造成结构连接处的疲劳破坏。因此,对波浪冲击建筑物过程的流场变化和力学特性的研究,有着重要的科学价值和实际意义。本文主要利用光滑粒子流体动力学方法(简称SPH方法,一种无网格方法)数值模拟位于浪溅区透空式结构物的波浪冲击问题,并结合物理模型试验,分析了影响波浪对水平板冲击的各种因素,以及冲击流场变化情况。具体内容包括:首先,本文将SPH方法引入到波浪与结构物相互作用的研究之中。对SPH方法的基本原理和数值实现过程进行详细论述,将亚格子湍流模型和Poisson方程迭代求解压力场的方法加入方程中,对流体的黏性和压力控制更加合理,能够准确的模拟波浪破碎时的湍流特性,以及波浪高速冲击结构物时产生的压力。重点对阻碍SPH方法发展的边界问题进行了深入的研究,对虚拟力法、镜像粒子法、虚拟粒子法、边界力法和固定边界粒子法等处理固定边界问题的方法进行了对比研究,分析各个方法的优缺点。并且,通过引入镜像的理念,改进了虚拟粒子法处理边界时的压力计算方法;同时,提出了一种新的边界压力计算方法(固定边界粒子法),通过实例验证了新方法的有效性和准确性,提高了边界压力的计算效率和精度。其次,建立了基于SPH方法的二维数值波浪水槽,对孤立波爬坡破碎、孤立波沿直墙爬高进行了数值模拟研究,并与实验结果进行对比分析,成功的模拟了孤立波破碎过程中先形成卷破波,之后,由于形成的射流水体下落所激发再次形成的卷破波,最后形成反向卷破波这样一个过程。另外,本文还对椭余波爬坡破碎进行了数值模拟研究,成功观察到了所谓的波扬现象。验证了本文基于SPH方法建立的数值水槽可以处理具有复杂自由面的水体大变形运动。第三,建立了基于SPH方法的孤立波和规则波与水平结构物相互作用的二维数值模型。系统的研究了规则波对二维水平板的冲击,得到了不同波高、周期和相对净空情况下,冲击压力在水平板下的分布情况,分析了二维水平板受力与波高、周期和相对净空的关系。通过与实验结果对比,以及对数值模拟结果的统计分析,使我们对波浪冲击压力的大小和分布规律有了进一步的认识。最后,进行了规则波对水平板冲击的三维试验研究,得到了不同波高、周期和相对净空情况下,冲击压力在三维水平板下的压力分布情况,分析了三维水平板受力与波高、周期和相对净空的关系。同时,建立了基于SPH方法的三维数值波浪水池,对规则波与三维水平板的相互作用问题进行了初步的数值模拟研究。更多还原

【Abstract】 With the exploitation of marine resources, the safety of coastal and offshore engineering structures, espcially wave impact on the strucures, has become the focus. In the process of wave slamming, the impact pressures with short duration and high peaks occurs when the waves hit the subface of the structure, which causes the destabilization of superstructure and the fratigue failure of joints. Hence, it is of great scientific value and pratical significance to do the research on the characteristics of flow field and pressures in the process of irregular wave impact.This dissertation, in terms of Smoothed Particle Hydrodynamics (SPH), presents the experimental investigation and numerical simulation of the slamming on the horizontal plate suspended over the water surface in the splash zone. It analyzes various factors that infuence the wave impact on horizontal plate and the intaneous velocity field of wave slamming.Firstly, SPH method is applied to the study of the interaction between waves and structures in this dissertation. It elaborates on the theory of SPH method and the process of numerical simulation. SPH method is improved by iterative soluting of Poisson equation for pressures field, and meanwhile introduces sub-grid turbulence model into the equation so as to more accurately describe the turbulence characteristics at the time of wave breaking and the pressures generated by the high-speed wave impact in this paper. Profound research is also made on boundary conditions. Through comparative study of five different solid boundary treatment methods, the advanteges and disadvantages of each method are analyzed. Besides, virtual particle method is improved with the introduction of mirror image theory. Meanwhile, a new solid boundary treatment method (solid boundary particle method) is provided, whose validity and precision is proved by means of experiments. Thus, the accuracy and computational efficiency of the pressures on the boundary is improved.Secondly, a numerical wave tank model is built on the basis of SPH method. A numerical simulation is implemented on solitary wave breaking on beaches and solitary wave ascending on the wall. Through the comparative analysis between the experiment and the results, it can be seen that the wave peak is at rather high speed, leading to the vertical shape of wave surface. The wave peak rushes in the form of a tongue until it falls into the water body below and a large number of bubbles are wrapped. Then wave splashes once again, presenting clear characteristics of wave breaking in form of a roller. Through the detailed analysis of the flow field and the impact pressures, we have a better understanding of the wave impact mechanism. At the same time, wave height rise of shallow-water waves is succesfully observed through the numerical simulation on cnoidal wave breaking on beaches.Thirdly, the two-dimensional numerical model of solitary wave and regular wave slamming to leveling board is built on the basis of SPH method. A systematic study is made on regular wave impact pressures on the two-dimensional horizontal deck, through which the distribution of wave impact pressures on the subface of the structure is achieved for different wave height, period and relative clearance and the relation between the impact pressures and wave height, period and relative clearance is analyzed. Through the comparison between the results of numerical and experimental data, we have a better understanding of the magnitude and the distribution rule of the regular wave impact pressures on the two-dimensional horizontal deck.Lastly, the three-dimensional experiment study is made on regular wave impact on horizontal plate. The distribution of wave impact pressures on three-dimensional structures is achieved for different wave height, period and relative clearance. The relation between the impact pressures and wave height, period and relative clearance is analyzed. Meanwhile, the three-dimensional numerical model is built on the basis of SPH method. An initial numerical simulation is performed on the interaction between regular wave and three-dimensional horizontal plate.更多还原