Physical experiments were conducted to examine the influence of adverse currents on the propagation of shallower water waves and their impact on the evolution of nonlinear wave shapes. Irregular waves, characterized by varying initial peak periods and amplitudes, were generated in a physical wave flume equipped with a bottom slope of 1/20. Three groups of spatially varying opposing currents were generated in the flume and interacted with the aforementioned wave trains. Experimental results confirm that strong opposing currents can significantly intensify local wave nonlinearity, thereby further influencing the deformation characteristics of waves. In contrast, a weak opposing current (without wave-blocking) has a negligible effect. Bicoherence analysis revealed that the degree of phase coupling among triads of waves increased with an elevated current velocity before wave-blocking. Nevertheless, during partial wave-blocking, the degree of phase coupling was seemingly weakened by an increase in opposing current. Moreover, the influence of a co-existing current in the formation of extreme waves was recognized. The study confirms that adverse currents notably affect extreme wave steepness and extreme wave skewness, with a negligible impact on extreme wave asymmetry. As a result, empirical formulas modified by current effects are presented, describing certain key nonlinear wave shapes as functions of the local Ursell number.

中文翻译：

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由于空间变化的相反电流而导致的非线性波形的实验室观察

通过物理实验来研究逆流对浅水波传播的影响及其对非线性波浪形状演变的影响。底部坡度为 1/20 的物理波槽中产生了以不同的初始峰值周期和振幅为特征的不规则波。水槽中产生三组空间变化的相反电流，并与上述波列相互作用。实验结果证实，强反向流会显着加剧局部波浪非线性，从而进一步影响波浪的变形特性。相反，弱的反向电流（没有波阻挡）的影响可以忽略不计。双相干分析表明，三波组之间的相位耦合程度随着波阻挡前水流速度的升高而增加。然而，在部分阻波期间，相位耦合程度似乎因反向电流的增加而减弱。此外，还认识到共存洋流对极端波浪形成的影响。研究证实，逆流显着影响极端波浪陡度和极端波浪偏斜度，而对极端波浪不对称性的影响可以忽略不计。因此，提出了经电流效应修改的经验公式，将某些关键的非线性波形描述为局部乌塞尔数的函数。