Abstract In this work, a grain-scale modelling technique is introduced for the simulation of unsaturated flow in deforming and swelling granular materials. To do so, a pore-scale model for unsaturated flow is coupled to the discrete element method (DEM). It is assumed that initially a dry packing of particles is quickly invaded by a liquid and becomes fully saturated. Particles start absorbing the liquid and this causes a rearrangement of particles, entrance of air into the packing, and a redistribution of the liquid (i.e. unsaturated flow). Flow was computed using a scheme of implicit pressure solver and explicit saturation update (IMPES), whilst particle movement was modelled using DEM. Simulations are continued until the packing is dry again. This is the first time that such a pore-scale model has been developed. We have used the model to investigate unsaturated flow during drying of a bed of swelling particles. Results indicated that the characteristic time scales of unsaturated flow and water absorption determine the swelling behaviour of the particle packing.

中文翻译：

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膨胀颗粒堆积中的不饱和流动；颗粒尺度模型

摘要 在这项工作中，引入了颗粒尺度建模技术来模拟变形和膨胀颗粒材料中的非饱和流动。为此，非饱和流动的孔隙尺度模型与离散元方法 (DEM) 相结合。假设最初干燥的颗粒堆积被液体迅速侵入并变得完全饱和。颗粒开始吸收液体，这会导致颗粒重新排列、空气进入填料以及液体的重新分布（即不饱和流）。流动使用隐式压力求解器和显式饱和度更新 (IMPES) 方案计算，而粒子运动使用 DEM 建模。继续模拟直到填料再次变干。这是第一次开发出这样的孔隙尺度模型。我们已经使用该模型研究了膨胀颗粒床干燥过程中的不饱和流动。结果表明，非饱和流动和吸水率的特征时间尺度决定了颗粒堆积的溶胀行为。