Particle-size segregation in self-channelized granular flows
Particle-size segregation in self-channelized granular flows
复制标题
自通道化颗粒流中的粒度分离
DOI：
10.1017/jfm.2022.1089
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发表时间：
2023
影响因子：
3.7
通讯作者：
Edwards A
中科院分区：
文献类型：
--
作者：
Edwards A
地球物理物质流，如泥石流，密集的火山碎屑流和雪崩可以自我渠道浅斜坡。形成的堤坝所提供的限制有助于保持流动深度，从而保持流动性，使自渠化流动比无限制的扩散流动更远。堤坝的形成和自我通道化与颗粒尺寸分离密切相关，但也可能发生在单分散流。本文使用罗查等人的单分散深度平均理论（J. Fluid Mech.，第876卷，2019年，pp. 591-641），其中包含滞后摩擦定律和二阶深度平均粘性项。这两个都是至关重要的形成一个行波，逐步沉积一对堤坝后面的前面。在假定Bagnold流动的情况下，在随波前移动的坐标系中重建了三维速度场。这使得一个双分散颗粒尺寸偏析理论被用来解决大，小颗粒浓度和颗粒路径在三维空间中，第一次。该模型表明，大颗粒倾向于分离到流的表面，形成一个甲壳，该甲壳在通道的中心，以及沿着外侧和堤坝墙的基础上延伸。小颗粒向下分离，并集中在主河道和内堤壁。这支持了低摩擦通道衬里提供了用于跳动增强的辅助机制的论点。它还表明，整个理论的尺度与颗粒直径，因此毫米级颗粒的实验提供了重要的见解，以岩石尺度的流动与巨石和较小的岩石碎片。该模型表明，自渠化并不需要颗粒尺寸偏析发生，但支持的假设，颗粒尺寸偏析和相关的摩擦反馈可以显着提高流动性和堤坝强度。
Geophysical mass flows such as debris flows, dense pyroclastic flows and snow avalanches can self-channelize on shallow slopes. The confinement afforded by formed levees helps to maintain the flow depth, and hence mobility, allowing self-channelized flows to run out significantly farther than unconfined, spreading flows. Levee formation and self-channelization are strongly associated with particle-size segregation, but can also occur in monodisperse flows. This paper uses the monodisperse depth-averaged theory of Rocha et al. (J. Fluid Mech., vol. 876, 2019, pp. 591–641), which incorporates a hysteretic friction law and second-order depth-averaged viscous terms. Both of these are vital for the formation of a travelling wave that progressively deposits a pair of levees just behind the front. The three-dimensional velocity field is reconstructed in a frame moving with the front assuming Bagnold flow. This enables a bidisperse particle-size segregation theory to be used to solve for the large and small particle concentrations and particle paths in three-dimensions, for the first time. The model shows that the large particles tend to segregate to the surface of the flow, forming a carapace that extends over the centre of the channel, as well as along the external sides and base of the levee walls. The small particles segregate downwards, and are concentrated in the main channel and in the inner levee walls. This supports the contention that a low-friction channel lining provides a secondary mechanism for run-out enhancement. It is also shown that the entire theory scales with particle diameter, so experiments with millimetre-sized particles provide important insights into geophysical-scale flows with boulders and smaller rock fragments. The model shows that self-channelization does not need particle-size segregation to occur, but supports the hypothesis that particle-size segregation and the associated frictional feedback can significantly enhance both the flow mobility and the levee strength.
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DOI：
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发表时间：
2012
期刊：
影响因子：
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影响因子：
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作者：
Edwards A
通讯作者：
Edwards A
DOI：
--
发表时间：
2015
期刊：
--
影响因子：
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作者：
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DOI：
--
发表时间：
2015
期刊：
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