ABSTRACT

In most of the current conventional tsunami numerical models, the steady flow friction law has been widely used to access the tsunami-induced bottom shear stress. However, according to our previous theoretical investigation showed that in almost the entire model domain from the tsunami source to the nearshore area, the tsunami-induced bottom boundary layer behaves like a wave boundary layer, rather than a quasi-steady flow boundary layer. The present study aims to develop a numerical method for tsunami simulation that elaborates a wave friction factor by implementing a correction method proposed by authors' previous work into the conventional 1D shallow water equation. As a result, the new method provides similar results to the original Manning method regarding the water level and the tsunami-induced velocity. However, the bottom shear stress estimated by the new method is higher than that from the Manning method over the entire computational domain. The transition locations from the wave friction zone to the steady friction zone are found at the water depth around 5 m under the present computational condition.

摘要

在目前大多数常规海啸数值模型中，稳流摩擦定律已被广泛用于获取海啸引起的底部剪应力。然而，根据我们之前的理论研究表明，在从海啸源到近岸地区的几乎整个模型域中，海啸诱发的底部边界层表现为波浪边界层，而不是准稳态流动边界层。本研究旨在开发一种用于海啸模拟的数值方法，该方法通过将作者先前工作提出的校正方法实施到传统的一维浅水方程中来阐述波浪摩擦系数。因此，新方法在水位和海啸引起的速度方面提供了与原始曼宁方法相似的结果。然而，在整个计算域上，新方法估计的底部剪应力高于曼宁方法。在目前的计算条件下，在5 m左右的水深处找到了从波浪摩擦带到稳定摩擦带的过渡位置。