Laboratory experiments on counter-propagating collisions of solitary waves. Part 2. Flow field
Laboratory experiments on counter-propagating collisions of solitary waves. Part 2. Flow field
复制标题
孤立波反向传播碰撞的实验室实验。
DOI：
10.1017/jfm.2014.427
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发表时间：
2014
影响因子：
3.7
通讯作者：
H. Yeh
中科院分区：
文献类型：
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作者：
Yongshuai Chen;E. Zhang;H. Yeh
摘要 在配套论文（Chen & Yeh，J. Fluid Mech.，第 749 卷，2014 年，第 577-596 页）中，通过分析测量的水面变化，对反向传播的孤立波的碰撞进行了实验研究。在这里，我们研究与碰撞相关的流场。利用实验室获得的解析速度数据，除了速度场之外，还可以根据加速度、涡度和速度梯度张量来分析流场。数据显示，在碰撞峰值前后，流动加速度达到最大值，这与预测碰撞峰值处最大加速度的线性理论不符。可视化的速度梯度张量场表明，流体团在达到最大波幅状态之前被垂直拉伸。碰撞峰值后，流体块在水平方向上被拉伸。讨论了基于涡量产生和扩散过程的边界层演化。结果表明，碰撞过程中床层发生了流动分离。碰撞产生小的色散尾波。尾随波的形成是通过观察速度梯度张量场的转变行为来捕获的：在尾随波的生成过程中，流体团的拉伸方向交替。
Abstract In the companion paper (Chen & Yeh, J. Fluid Mech., vol. 749, 2014, pp. 577–596), collisions of counter-propagating solitary waves were studied experimentally by analysing the measured water-surface variations. Here we study the flow fields associated with the collisions. With the resolved velocity data obtained in the laboratory, the flow fields are analysed in terms of acceleration, vorticity, and velocity-gradient tensors in addition to the velocity field. The data show that flow acceleration becomes maximum slightly before and after the collision peak, not in accord with the linear theory which predicts the maximum acceleration at the collision peak. Visualized velocity-gradient-tensor fields show that fluid parcels are stretched vertically prior to reaching the state of maximum wave amplitude. After the collision peak, fluid parcels are stretched in the horizontal direction. The boundary-layer evolution based on the vorticity generation and diffusion processes are discussed. It is shown that flow separation occurs at the bed during the collision. The collision creates small dispersive trailing waves. The formation of the trailing waves is captured by observing the transition behaviour of the velocity-gradient-tensor field: the direction of stretching of fluid parcels alternates during the generation of the trailing waves.