ABSTRACT

In numerical simulations for large-scale coastal environments, it is crucial to accurately reproduce internal Kelvin and Poincare waves under Coriolis forcing. Therefore, for surface waves, the effects of horizontal grid representation on Kelvin and Poincare waves have been investigated using both structured and unstructured grid models. However, the effect of the grid representation on internal waves is poorly understood so far, especially for structured grids which uses a step-like lateral boundary. This study thus investigates the applicability of structured grids into internal Kelvin and Poincare waves using a circular basin to exclude the effect of open boundaries and discusses numerical errors in terms of the Rosbby-grid factor. Several grid sizes were used for a structured grid simulation, which demonstrated that the structured grid simulation reproduced the internal Kelvin and Poincare waves sufficiently accurately compared to those obtained by the unstructured grid simulation. Furthermore, the structured grid simulation was also confirmed to agree very well with the unstructured grid simulation in a conical basin which exhibits more realistic geometry. It was thereby shown the possibility that internal waves can be accurately analyzed using structured grids when the Rossby-grid factor is more than 10.

摘要

在大规模沿海环境的数值模拟中，准确再现科里奥利强迫下的内部开尔文波和庞加莱波至关重要。因此，对于表面波，已经使用结构化和非结构化网格模型研究了水平网格表示对开尔文和庞加莱波的影响。然而，到目前为止，人们对网格表示对内波的影响知之甚少，尤其是对于使用阶梯状横向边界的结构化网格。因此，本研究使用圆形盆地来研究结构化网格在内部开尔文波和庞加莱波中的适用性，以排除开放边界的影响，并根据 Rosbby 网格因子讨论数值误差。几种网格尺寸用于结构化网格模拟，这表明与非结构化网格模拟获得的那些相比，结构化网格模拟充分准确地再现了内部开尔文和庞加莱波。此外，结构化网格模拟也被证实与锥形盆地中的非结构化网格模拟非常吻合，圆锥形盆地表现出更逼真的几何形状。由此表明，当 Rossby 网格因子大于 10 时，可以使用结构化网格准确分析内波。