Grain-resolving simulations of submerged cohesive granular collapse
Grain-resolving simulations of submerged cohesive granular collapse
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DOI：
10.1017/jfm.2022.404
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发表时间：
2022-05
影响因子：
3.7
通讯作者：
R. Zhu;Zhiguo He;K. Zhao;B. Vowinckel;E. Meiburg
中科院分区：
文献类型：
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作者：
R. Zhu;Zhiguo He;K. Zhao;B. Vowinckel;E. Meiburg
摘要通过颗粒解析直接数值模拟，研究了弱多分散、松散堆积的粘性颗粒柱在水下崩塌时的长径比和黏结力强度的函数关系。粘结力的作用是防止单个颗粒脱离坍塌柱的主体，降低其前缘速度，并产生更短、更厚的最终沉积物。所有这些效应都可以通过分段幂律关系在广泛的参数范围内准确地捕捉到。内聚力大大减少了粒子释放的可用势能。对于浅柱，颗粒和流体动能减小，内聚力增强。另一方面，对于高柱，适度的内聚力增加了最大颗粒动能，因为它们加速了上部柱段的初始自由落体。只有当黏结力较大时，粒子的峰值动能才会减小。计算粒子跟踪表明，内聚力减少了坍塌柱内粒子的混合，并确定了那些移动最远的粒子的起源区域。模拟结果表明，内聚促进了聚集和聚集体的形成。此外，它们还提供了有关内聚力和直接接触力键的时间和空间演变网络的完整信息。虽然法向接触力主要在垂直方向上对齐，但在整个坍塌过程中，内聚键会调整其首选的空间方向。它们产生的净宏观应力抵消了变形，减缓了前进的颗粒锋的扩散。
Abstract We investigate the submerged collapse of weakly polydisperse, loosely packed cohesive granular columns, as a function of aspect ratio and cohesive force strength, via grain-resolving direct numerical simulations. The cohesive forces act to prevent the detachment of individual particles from the main body of the collapsing column, reduce its front velocity, and yield a shorter and thicker final deposit. All of these effects can be captured accurately across a broad range of parameters by piecewise power-law relationships. The cohesive forces reduce significantly the amount of available potential energy released by the particles. For shallow columns, the particle and fluid kinetic energy decreases for stronger cohesion. For tall columns, on the other hand, moderate cohesive forces increase the maximum particle kinetic energy, since they accelerate the initial free-fall of the upper column section. Only for larger cohesive forces does the peak kinetic energy of the particles decrease. Computational particle tracking indicates that the cohesive forces reduce the mixing of particles within the collapsing column, and it identifies the regions of origin of those particles that travel the farthest. The simulations demonstrate that cohesion promotes aggregation and the formation of aggregates. Furthermore, they provide complete information on the temporally and spatially evolving network of cohesive and direct contact force bonds. While the normal contact forces are aligned primarily in the vertical direction, the cohesive bonds adjust their preferred spatial orientation throughout the collapse. They result in a net macroscopic stress that counteracts deformation and slows the spreading of the advancing particle front.