双孤立波爬高的数值模拟

发布时间：2018-06-08 01:41

本文选题：海啸 + 孤立波　；参考：《上海交通大学》2015年硕士论文

【摘要】：海啸是自然界破坏力极强的海洋灾害之一,主要是由海底强地震、外来陨石撞击等所引发的。各种海啸的诱因均伴随有深海水体的剧烈垂向运动。在深海中海啸波高虽然不大,但其能力集中并且传播速度极快,在海啸波传至近岸时,往往由于水深急剧变浅,波高陡增,在海湾及港口内引起海水的巨大波动或振荡,巨浪冲上陆地,淹没岸边,摧毁建筑物,成为严重灾害,而其中海啸波在海岸和陆地上的爬高是造成陆地上破坏最直接的方式。本文基于RANS方程、VOF方法以及修正的Goring造波方法建立了模拟活塞式推波板运动的二维数值波浪水槽,实现了孤立波爬高的数值模拟。利用运动物体动边界模拟造波机推波板的运动,有效地实现了单孤立波以及不同波峰间距双孤立波的造波方法。首先通过基本的算例验证数值波浪水槽的可靠性,结果表明:改进的孤立波造波方法与目标波形吻合较好,多组不同相对波高的单孤立波爬高极值与现有的理论值和实验值均较接近;双孤立波直墙爬高数值计算结果表明双孤立波在传播过程中与实验值基本一致,且具有较好的稳定性,数值模拟的结果与实验结果基本一致。在一定的地形条件下,海啸波在近海传播过程中有可能会演化成若干个孤立波组成的波列。为了了解多个孤立波波列对海岸结构物的作用机理,在数值波浪水槽中进行了双孤立波的斜坡爬高实验。在复验了孤立波直墙爬高的基础上,设计了多种波高组合作为目标波形,根据所得数据进一步研究双孤立波两个爬高极值的变化规律,以及这些变化与入射波高和双孤立波两个波峰间相对距离的关系,同时针对等波高的双孤立波,研究其速度场及能量转化规律。数值模拟结果表明:对于等波高的双孤立波,当入射波波高较大及两个波峰间距相对较小时,跟随在后孤立波的爬高放大系数小于先导孤立波的爬高放大系数;双孤立波在爬高过程中,波动场的势能时间过程线呈现三峰形态,其中居中的最大势能峰值出现在第二个孤立波与经斜坡反射后反向传播的第一个孤立波完全对撞的时刻;同时在斜坡角度较小时,双孤立波的一个孤立波动能完全转化为势能是先于该波在斜坡上爬到最高点,而斜坡角度增大至到直墙时,双孤立波的一个孤立波动能完全转化为势能和该波在斜坡上爬到最高点是同一时刻。
[Abstract]:Tsunami is one of the most destructive marine disasters in nature, which is mainly caused by strong submarine earthquakes and impact of foreign meteorites. The causes of various tsunamis are accompanied by intense vertical motion of deep sea waters. Although the tsunami wave height is not large in the deep sea, its ability is concentrated and its propagation speed is extremely fast. When the tsunami wave reaches the shore, it often causes a huge fluctuation or oscillation of the sea water in the bay and port due to the sharp shallowness of the water depth and the sharp increase of the wave height. Huge waves have washed up the land, flooded the shore, destroyed buildings, and become a serious disaster, and the tsunami wave climbing on the shore and land is the most direct way to cause damage on the land. Based on the Rans equation and the modified Goring method, a two-dimensional numerical wave flume is established to simulate the motion of the piston plate. The numerical simulation of the solitary wave climbing is realized. In this paper, the moving boundary of moving object is used to simulate the motion of the wave plate of the wave-maker, and the method of generating single solitary wave and double solitary wave with different crest spacing is realized effectively. The reliability of numerical wave flume is verified by a basic example. The results show that the improved solitary wave generating method is in good agreement with the target waveform. The single solitary wave climbing extremum of several groups of different relative wave heights is close to the existing theoretical and experimental values, and the numerical results of double solitary wave vertical wall climbing show that the double solitary wave is basically consistent with the experimental value in the process of propagation. The numerical simulation results are in good agreement with the experimental results. Under certain topographic conditions, the tsunami wave may evolve into a series of solitary waves in the course of offshore propagation. In order to understand the action mechanism of several solitary wave trains on coastal structures, a slope climbing experiment of double solitary waves was carried out in a numerical wave tank. On the basis of the repeated inspection of the climbing of the straight wall of solitary waves, several wave height combinations are designed as the target waveforms. According to the obtained data, the variation law of the two climbing extremum of the double solitary waves is further studied. The relationship between these variations and the relative distance between two peaks of incident wave height and double solitary wave is also discussed. The velocity field and energy transformation law of double solitary wave with equal wave height are studied at the same time. The numerical simulation results show that when the incident wave height is large and the distance between the two peaks is relatively small, the magnification factor of the following solitary wave is smaller than that of the leading solitary wave. In the process of double solitary wave climbing, the time line of potential energy of the wave field presents three peaks, in which the middle maximum potential energy peak appears at the time when the second solitary wave completely collides with the first solitary wave propagating backward through the slope; At the same time, when the angle of the slope is small, an isolated wave of the double solitary wave can be completely converted into the potential energy when the wave climbs to the highest point on the slope before the wave, and the angle of the slope increases to the straight wall. An isolated wave of a double solitary wave can be converted into potential energy at the same time as the wave climbs to the highest point on the slope.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P731.25

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