Dry granular materials have been the subject of many investigations, while wet granular materials, which widely exist in many real-world applications, have only received limited attention. The aim of this paper is to address the missing gap in continuum modeling of wet granular materials. To study the wet granular flows, a grain-scale capillary interaction is introduced, as additional cohesive stress in the continuum-scale framework. We coupled the viscoplastic constitutive law for dry granular material and cohesion model for wet isotropic granular material to capture the behavior of wet granular materials. This combined model is implemented in a smooth particle hydrodynamics framework because the meshfree nature of this method captures the large deformation of granular flows without local grid distortion. The Wendland kernel is used as the interpolation kernel to improve numerical stability. This framework is validated by comparing numerical results with recent experimental findings for both dry and wet cases. The comparisons are illustrative of the potential of the framework to capture the behavior of granular materials across different phases. For different levels of friction and water content, the run-out dynamics and shear strength properties of granular materials in the final quasi-static regime are investigated. For granular flows on flat surfaces, compared with dry granular materials, with the introduction of surface tension in wet granular materials, it is found that there are increases in shear stresses locally and globally, enabling stronger internal forces to support structures with larger angles of repose. The surface energy-induced cohesion is found to play an important role in low friction cases compared to high friction cases. To benchmark the numerical framework presented here, granular column collapses on curved surfaces are also investigated. For flows on curved surfaces, although there are also increases in internal shear stresses, the differences in final profiles between wet granular materials and dry granular materials are not as pronounced as that on flat surfaces due to geometric constraints. The findings of this work are demonstrative of the capabilities of the smooth particle hydrodynamics method for the study of wet granular materials. This effort can serve as a step forward in the quest for a unified continuum theory and computational framework of granular material dynamics.

中文翻译：

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湿颗粒柱塌陷的光滑颗粒流体动力学研究

干颗粒材料一直是许多研究的主题，而在许多实际应用中广泛存在的湿颗粒材料仅受到了有限的关注。本文的目的是解决湿颗粒材料连续模型建模中缺失的空白。为了研究湿颗粒流，引入了颗粒级毛细相互作用，作为连续量级框架中的附加内聚应力。我们结合了干颗粒材料的粘塑性本构定律和湿各向同性颗粒材料的内聚模型，以捕获湿颗粒材料的行为。该组合模型是在光滑的粒子流体动力学框架中实现的，因为该方法的无网格性质捕获了颗粒流的大变形而没有局部网格失真。Wendland内核用作插值内核，以提高数值稳定性。通过比较数值结果和最近在干燥和潮湿情况下的实验发现，验证了该框架的有效性。这些比较说明了该框架在不同阶段捕获粒状材料行为的潜力。对于不同水平的摩擦和含水量，研究了最终准静态状态下颗粒材料的跳动动力学和抗剪强度特性。与干颗粒材料相比，在平坦表面上的颗粒流动与湿颗粒材料中引入的表面张力相比，发现局部和全局剪切应力增加，从而使更强的内力能够支撑具有较大休止角的结构。与低摩擦情况相比，发现在低摩擦情况下表面能引起的内聚力起着重要作用。为了对这里提出的数值框架进行基准测试，还研究了曲面上的颗粒状柱塌陷。对于弯曲表面上的流动，尽管内部剪切应力也有所增加，但由于几何约束，湿颗粒材料和干颗粒材料之间的最终轮廓差异不如平坦表面上的明显。这项工作的发现证明了光滑颗粒流体动力学方法对湿颗粒材料研究的能力。这项工作可以作为对颗粒材料动力学统一统一理论和计算框架的探索的一步。