Mechanics of the granular rapid subaerial flow(pyroclastic flow and snow avalanche)

颗粒状快速地下流的力学（火山碎屑流和雪崩）

基本信息

批准号：
08458102
负责人：
TAKAHASHI Tamotsu
金额：
$ 2.69万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08458102/
关键词：
granular flow particle collision momentum transport pyroclastic flow nue ardente fluidization snow avalanche snow ball 衝突熱風

项目摘要

This research aims to present the unified theory of the flow of both the pyroclastic flow and the snow avalanche and to make possible to numerically simulate the actual phenomena.First, the constitutive equations for the granular flow which take the inelastic collision, the kinetic momentum transport and static skeleton stress into account are deduced. Then, those equations are extended to a resistance to flow formula to explain the characteristic behaviors of the experimentally obtained laminar, laminar/dispersive and dispersive type flows.This theory is applied to the Merapi type pyroclastic flow that occurred at the Fugendake, Unzen volcano. The processes of breaking the fallen lava dome into fragment and the flow of those pyroclastic material are satisfactory explained. Quantitative mechanism of formation, flow behaviors and the stoppage of the main basal fluidized layr and the nue 'ardent' part upon the basal layr which are the characteristic structure of the pyroclastic flow are made clear. A numerical simulation model based on the theory can explain the actual limits of flow as well as the distribution of the thickness of deposit within the area.Processes of snow ball formation and the effects of snow balls to the characteristics of the flow are quantitatively explained by the granular flow theory. Moreover, the effect of the snow temperature to the formation of snow balls and the process of erosion and deposition are taken into account in the numerical simulation model. The model is applied to the 1986 Maseguchi snow avalanche (powder snow avalanche) and the 1992 Hakubadake avalanche (we snow avalanche) and the reporductions of both two phenomena are very good.

本研究旨在提出火山碎屑流和雪崩流动的统一理论，并使数值模拟实际现象成为可能。首先，考虑非弹性碰撞、动量传递的颗粒流本构方程推导出考虑静态骨架应力。然后，将这些方程扩展到流阻公式，以解释实验获得的层流、层流/分散和分散型流的特征行为。该理论应用于发生在云仙火山 Fugendake 的 Merapi 型火山碎屑流。塌陷的熔岩穹顶破碎成碎片的过程以及这些火山碎屑物质的流动得到了令人满意的解释。明确了火山碎屑流特征结构的主要基底流化层和基底层上的核心“热”部分的形成、流动行为和停止的定量机制。基于该理论的数值模拟模型可以解释水流的实际极限以及区域内沉积物厚度的分布。雪球形成过程以及雪球对水流特性的影响可以通过颗粒流理论。此外，数值模拟模型还考虑了雪温对雪球形成的影响以及侵蚀和沉积过程。该模型应用于1986年马濑口雪崩（粉雪雪崩）和1992年白马岳雪崩（雪崩），两种现象的再现都非常好。