内孤立波沿缓坡地形传播特性的实验研究

以南中国海东北部海域底部缓坡地形为背景, 在大型重力式分层流水槽中模拟了下凹型内孤立波沿缓坡地形传播过程中的浅化、破碎、分裂等现象, 利用分层染色标识方法和多点组合探头阵列技术对内孤立波沿缓坡地形演化特征进行了定性分析和定量测量. 实验表明: 浅化效应使内孤立波传播速度减小, 对大振幅内孤立波具有抑制作用, 对小振幅波具有放大效应; 浅化效应可导致内孤立波的剪切失稳及破碎, 还可导致大振幅内孤立波的分裂. 利用Miles稳定性理论可定性描述内孤立波沿缓坡地形传播时发生不稳定状态的位置, 实验结果与理论分析相符合. 关键词： 分层流 缓坡地形 内孤立波 不稳定性

Experimental investigations on the propagation characteristics of internal solitary waves over a gentle slope

In a stratified fluid tank, experiments on the propagating, shoaling and breaking of the internal solitary waves over a gentle slope similar to the topography in the northeast of the South China Sea are conducted. The qualitative analysis on the evolving characteristics of the internal solitary waves is accomplished by use of the dye-tracing technique, and their quantitative measurement is carried out by using the multi-channel conductivity-probe arrays. It is shown that due to the shoaling effect the internal solitary waves with large amplitude are restrained, but the waves with small amplitude are magnified. The shoaling effect will also lead to the decrease of the propagation velocity of the internal solitary waves. Further, the shoaling effect will bring about strong shear flow instability, and then makes the internal solitary wave broken. The breaking wave will result in the fission from one large amplitude wave into several small amplitude waves with the same polarity. By means of the Mile's stability theory, the instable happening-location of the internal solitary wave over the gentle slope can be described through the Richardson number. The experimental results accord well with the theoretical analyses.