A coupled CFD-DEM analysis of granular flow impacting on a water reservoir
A coupled CFD-DEM analysis of granular flow impacting on a water reservoir
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DOI：
10.1007/s00707-014-1119-z
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发表时间：
2014-04
期刊：
影响因子：
2.7
通讯作者：
Tong Shan;Jidong Zhao
中科院分区：
文献类型：
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作者：
Tong Shan;Jidong Zhao
大量的泥石流或岩石崩塌落入水库可能会造成毁灭性的危害，如漫顶或溃坝。本文采用计算流体力学与离散元法耦合的方法，对颗粒流从倾斜斜坡落入水库的冲击特性进行了分析。CFD和DEM之间的耦合考虑了诸如浮力、拖曳力和虚拟质量力等重要的流体-颗粒相互作用力。研究发现，水库中的水的存在通常可以帮助减少颗粒流对水库后面的淤地坝的直接冲击，最大限度地减少颗粒之间的激烈碰撞和弹跳，并有助于形成更均匀的最终沉积堆相比，干燥的情况。在干颗粒流中，颗粒间的摩擦和碰撞是能量耗散的主要因素，而在湿颗粒流中，颗粒系统的大部分动能首先传递给水体，使颗粒流本身成为一个以接触剪切为主的流，并在淤地坝和坡面之间形成一个相当持续的冲击波，然后才沉降下来。幂律分布的颗粒流的速度剖面上的斜坡和水库地面，它可能会暂时改变到一个线性分布的过渡点的坡脚的萨维奇数描绘一个峰值。考虑颗粒间的滚动摩擦，可以均匀地降低颗粒流的运动速度，减轻对淤地坝的整体冲击。对淤地坝的影响取决于初始排沙高度和库水位。已经发现，当最初的碎片高度相对较高时，水库中的中等水位一般比较安全。
Massive debris flows or rock avalanches falling into a water reservoir may cause devastating hazards such as overtopping or dam breakage. This paper presents a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) analysis on the impacting behaviour of a granular flow falling from an inclined slope into a water reservoir. The coupling between CFD and DEM considers such important fluid–particle interaction forces as the buoyancy force, the drag force and the virtual mass force. It is found that the presence of water in the reservoir can generally help to reduce direct impact of granular flow on the check dam behind the reservoir, minimizes the intense collisions and bouncing among particles and helps form a more homogeneous final deposited heap as compared to the dry case. While the interparticle/particle–wall frictions and collisions dominate the energy dissipation in the dry granular flow, the majority of kinetic energy of the granular system in the wet case is first transferred to the water body, which leaves the granular flow itself to become a contact-shearing dominant one and causes impulse wave travelling between the check dam and the slope surface for a rather sustained period before settling down. A power law distribution is found for the velocity profile of the granular flow travelling on both the slope and the reservoir ground surfaces, and it may change temporarily to a linear distribution at the transition point of the slope toe where the Savage number depicts a peak. The consideration of rolling friction among particles may homogeneously reduce the travelling velocity of the granular flow and alleviate the overall impact on the check dam. The impact on the check dam depends on both the initial debris releasing height and the reservoir water level. Medium water levels in the reservoir have been found to be generally safer when the initial debris height is relatively high.