The tsunami generation potential of pyroclastic density currents (PDCs) entering the sea is poorly understood, due to limited data and observations. Thus far, tsunami generation by PDCs has been modeled in a similar manner to tsunami generation associated with landslides or debris flows, using two-layer depth-averaged approaches. Using the adaptive partial differential equation solver Basilisk and benchmarking with published laboratory experiments, this work explores some of the important parameters not yet accounted for in numerical models of PDC-generated tsunamis. We use assumptions derived from experimental literature to approximate the granular, basal flow component of a PDC as a dense Newtonian fluid flowing down an inclined plane. This modeling provides insight into how the boundary condition of the slope and the viscosity of the dense granular-fluid influence the characteristics of the waves generated. It is shown that the boundary condition of the slope has a first-order impact on the interaction dynamics between the fluidized granular flow and water, as well as the energy transfer from the flow to the generated wave. The experimental physics is captured well in the numerical model, which confirms the underlying assumption of Newtonian fluid-like behavior in the context of wave generation. The results from this study suggest the importance of considering vertical density and velocity stratification in wave generation models. Furthermore, we demonstrate that granular-fluids denser than water are capable of shearing the water surface and generating significant amplitude waves, despite vigorous overturning.

中文翻译：

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流体化颗粒流进入水中的数值模拟：通过火山碎屑密度流模拟海啸生成的见解

由于数据和观测有限，人们对进入海洋的火山碎屑密度流 (PDC) 的海啸产生潜力知之甚少。迄今为止，已使用两层深度平均方法以类似于与滑坡或泥石流相关的海啸产生的方式对 PDC 产生的海啸进行建模。使用自适应偏微分方程求解器 Basilisk 和已发表的实验室实验进行基准测试，这项工作探索了一些尚未在 PDC 产生的海啸数值模型中考虑的重要参数。我们使用从实验文献中得出的假设将 PDC 的颗粒状、基础流分量近似为沿斜面流动的稠密牛顿流体。这种建模可以深入了解斜坡的边界条件和致密颗粒流体的粘度如何影响所产生的波的特性。结果表明，边坡边界条件对流化颗粒流与水的相互作用动力学以及从流动到产生波的能量传递具有一阶影响。数值模型很好地捕捉了实验物理学，这证实了在波浪产生的背景下牛顿流体状行为的基本假设。这项研究的结果表明在波浪生成模型中考虑垂直密度和速度分层的重要性。此外，