Abstract The behaviour of dry and wet volcanic granular flows is one of the main research topics in present day geophysics and volcanology. It involves various disciplines (e.g. sedimentology, geophysics, fluid dynamics) and investigation techniques (e.g. field studies, laboratory experiments, computational fluid dynamics). The vast interest is justified by the complex nature of these flows and their very dangerous nature that threaten millions of people around the world. In the last decade, computational fluid dynamics has become one of the main instruments used to reproduce past events of volcanic granular flows or to predict their behaviour and potential hazard. In this study, we tested two of the most used codes for simulating volcanic granular flows, TITAN2D and FLO2D, against well studied natural cases (the 1998 wet granular flows in the Sarno area and the 2005 block and ash flows at Colima volcano) and large-scale experiments on granular flows. Comparison between simulated parameters and real ones were carried out in order to evaluate strengths and weaknesses of the two numerical codes. TITAN2D results showed how the basal friction angle is fundamental to control numerical simulations and its dependence on the topographic complexities, DEM resolution and slope-angle ratio. Simulation of large scale experiments offered a good relationship between slope angle ratio at break in slope and basal friction angle, which is useful for application to small drainage basins with not complex channel morphology. FLO2D suffers the lack of rheometric parameters for volcaniclastic material, but is less sensitive of DEM resolution with respect to TITAN2D.

中文翻译：

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火山颗粒流的浅水模型：TITAN2D 和 FLO2D 数值代码的优缺点综述

摘要 干湿火山颗粒流的行为是当今地球物理学和火山学的主要研究课题之一。它涉及各种学科（例如沉积学、地球物理学、流体动力学）和调查技术（例如实地研究、实验室实验、计算流体动力学）。这些流动的复杂性质及其对全世界数百万人构成威胁的非常危险的性质证明了巨大的兴趣是合理的。在过去十年中，计算流体动力学已成为用于重现火山颗粒流过去事件或预测其行为和潜在危害的主要工具之一。在这项研究中，我们测试了两个最常用的模拟火山颗粒流的代码，TITAN2D 和 FLO2D，与经过充分研究的自然情况（Sarno 地区 1998 年的湿颗粒流和 2005 年科利马火山的块和灰流）和颗粒流的大规模实验相比较。对模拟参数和实际参数进行了比较，以评估两种数值代码的优缺点。TITAN2D 结果表明基础摩擦角是控制数值模拟的基础及其对地形复杂性、DEM 分辨率和斜角比的依赖性。大型试验模拟表明，边坡断裂坡角比与基底摩擦角关系良好，适用于河道形态不复杂的小型流域。FLO2D 缺乏火山碎屑材料的流变参数，