Abstract The breaking properties of internal solitary waves (ISWs) flowing over a bottom step were investigated experimentally. The experiments were performed in a two-layer immiscible system to avoid the influence of diffusion and mixing. The flat bottom condition and the bottom step condition had been conducted respectively. The characteristics of incident ISWs, the process of breaking and the subsequent developments were taken into discussion. A modified internal Iribarren number was introduced, and the critical condition of breaking was considered to be related to its trend change point. The initial stage of the breaking process was found can be divided into spatially discrete characteristic structures other than messy flowing of the full interface. And the characteristic structures have close horizontal lengths for different amplitudes. The horizontal velocity gradient was identified as the key parameter of shear instability. By analyzing the subsequent developments, the completely broken ISWs were found can reform a quasi ISWs propagating upon the bottom step which has a smooth front-face and an ever-breaking back-face. Due to the breaking of the back-face, the amplitude of reformed ISWs continues to decrease. Meanwhile, the attenuation rate was noticed to be related to the incident amplitude, but not be related to whether it is broken or the degree of breaking.

中文翻译：

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流过底部台阶的内部孤立波破碎特性的实验研究

摘要 通过实验研究了流过底部台阶的内部孤立波（ISW）的破碎特性。实验在两层不混溶体系中进行，以避免扩散和混合的影响。分别进行了平底条件和底部台阶条件。讨论了事件ISW的特征、破解过程和随后的发展。引入了一个修正的内部 Iribarren 数，认为突破的临界条件与其趋势变化点有关。发现破碎过程的初始阶段除了整个界面的凌乱流动外，还可以分为空间离散的特征结构。并且特征结构对于不同的幅度具有接近的水平长度。水平速度梯度被确定为剪切不稳定的关键参数。通过分析随后的发展，发现完全破碎的ISWs可以改造一个准ISWs在底部阶梯上传播，具有光滑的正面和不断破碎的背面。由于背面的断裂，重整的ISWs的幅度继续减小。同时，注意到衰减率与入射幅度有关，但与是否破裂或破裂程度无关。改革后的ISWs的幅度继续下降。同时，注意到衰减率与入射幅度有关，但与是否破裂或破裂程度无关。改革后的ISWs的幅度继续下降。同时，注意到衰减率与入射幅度有关，但与是否破裂或破裂程度无关。