A two-phase SPH model for massive sediment motion in free surface flows
A two-phase SPH model for massive sediment motion in free surface flows
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DOI：
10.1016/j.advwatres.2019.05.006
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发表时间：
2019-07
影响因子：
4.7
通讯作者：
Huabin Shi;Pengfei Si;P. Dong;Xiping Yu
中科院分区：
文献类型：
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作者：
Huabin Shi;Pengfei Si;P. Dong;Xiping Yu
有自由面水体中的大颗粒泥沙运动是一种重要的地球物理运动，如河口三角洲的高含沙河流和水下滑坡产生的浊流等。这种流动的一个关键和共同的特点是，水和泥沙之间的相互作用以及泥沙颗粒之间的相互作用在影响泥沙运动和流体流动方面同样重要。本文提出了一种数值模型，该模型建立在早期基于固液混合物连续体公式的两相SPH模型的基础上并对其进行了扩展（Shi等人，2017年），以提供一个统一的描述大量的泥沙运动在自由表面流。在该模型中，本构关系的基础上的稠密颗粒流的流变学被引入来表示的颗粒间的应力，而相间的拖曳力被确定相结合的Ergun方程的稠密固体-流体混合物和稀悬浮液的幂律。该模型首次应用于水中松散或密集堆积颗粒柱的坍塌研究。计算的颗粒柱的表面轮廓与实验数据吻合良好。结果表明，由于水沙相互作用过程的不同，松散堆积柱和密集堆积柱的表现也有很大差异。然后，该模型被用来模拟溃坝流的移动的沉积物床。计算得到的流动形态和动床形态也与实测数据吻合较好。在流动前缘的预测位置的平均误差为0.8%，而最大床高的平均误差为12.9%。为了进一步确定所涉及的动态过程，水沙相互作用对床料运动的影响进行了研究，通过检查的空间和时间变化的压力和流速。应用结果表明，所提出的两相SPH模型能够成功地模拟重力驱动的水下颗粒流和剪切流驱动的强烈输沙，在两种水流同时存在的实际情况下具有潜在的应用价值，如浅海风暴引发的滑坡和导致堤坝溃决的水流。
Massive sediment motion in water with a free surface is an important kind of geophysical flows such as hyper-concentrated sediment laden river flows discharging into estuarine delta and turbidity currents generated by subaqueous landslides. One of the key and common characteristics of such flows is that interactions between water and sediment as well as those among sediment particles are equally important in affecting the sediment motion and the fluid flow. This paper presents a numerical model that builds on and extends an earlier two-phase SPH model based on a continuum formulation of solid-liquid mixtures (Shi et al., 2017) to provide a unified description of massive sediment motion in free surface flows. In the model, a constitutive law based on the rheology of dense granular flow is introduced to express the intergranular stresses while the interphase drag force is determined by combining the Ergun equation for dense solid-fluid mixtures and the power law for dilute suspensions. The proposed model is firstly applied to the study of collapse of loosely or densely packed granular columns submerged in water. The computed surface profiles of the granular column are found to be in good agreement with the experimental data. It shows that the loosely packed and the densely packed columns behave rather differently due to the differences in water-sediment interaction processes. The model is then used to simulate a dam-break flow over a mobile sediment bed. The computed configurations of the flow and the movable bed also agree well with the measured data. The predicted position on the leading edge of the flow has a mean error of 0.8% while the mean error for the maximum bed height is 12.9%. To further identify the dynamic processes involved, effects of water-sediment interactions on the motion of bed materials are investigated by examining the spatial and temporal variations of pressure and flow velocity. As shown in the applications, the proposed two-phase SPH model can successfully represent both the gravity-driven underwater granular flows and the shear flow driven intense sediment transport, implying its potential use in practical scenarios in which the two kinds of flows exist simultaneously, such as landslides triggered by storm in shallow sea and flows resulted in barrier or dam breaks.