Zhu Siyu, Wu Chunlin, Yin Huiming
Department of Civil Engineering and Engineering Mechanics, Columbia University, 610 S.W. Mudd, 500 West 120th Street, New York, NY 10027, USA.
Materials (Basel). 2021 Apr 25;14(9):2199. doi: 10.3390/ma14092199.
Particle mixing process is critical for the design and quality control of concrete and composite production. This paper develops an algorithm to simulate the high-shear mixing process of a granular flow containing a high proportion of solid particles mixed in a liquid. DEM is employed to simulate solid particle interactions; whereas SPH is implemented to simulate the liquid particles. The two-way coupling force between SPH and DEM particles is used to evaluate the solid-liquid interaction of a multi-phase flow. Using Darcy's Law, this paper evaluates the coupling force as a function of local mixture porosity. After the model is verified by two benchmark case studies, i.e., a solid particle moving in a liquid and fluid flowing through a porous medium, this method is applied to a high shear mixing problem of two types of solid particles mixed in a viscous liquid by a four-bladed mixer. A homogeneity metric is introduced to characterize the mixing quality of the particulate mixture. The virtual experiments with the present algorithm show that adding more liquid or increasing liquid viscosity slows down the mixing process for a high solid load mix. Although the solid particles can be mixed well eventually, the liquid distribution is not homogeneous, especially when the viscosity of liquid is low. The present SPH-DEM model is versatile and suitable for virtual experiments of particle mixing process with different blades, solid particle densities and sizes, and liquid binders, and thus can expedite the design and development of concrete materials and particulate composites.
颗粒混合过程对于混凝土和复合材料生产的设计及质量控制至关重要。本文开发了一种算法，用于模拟在液体中混入高比例固体颗粒的颗粒流的高剪切混合过程。采用离散单元法（DEM）模拟固体颗粒间的相互作用；而采用光滑粒子流体动力学方法（SPH）模拟液体颗粒。SPH与DEM颗粒之间的双向耦合力用于评估多相流的固液相互作用。本文利用达西定律，将耦合力评估为局部混合孔隙率的函数。在通过两个基准案例研究（即固体颗粒在液体中移动以及流体流经多孔介质）对模型进行验证后，将该方法应用于由四叶搅拌器在粘性液体中混合两种固体颗粒的高剪切混合问题。引入了一个均匀性度量来表征颗粒混合物的混合质量。采用本算法进行的虚拟实验表明，对于高固体负载混合物，添加更多液体或增加液体粘度会减缓混合过程。尽管固体颗粒最终可以很好地混合，但液体分布并不均匀，尤其是当液体粘度较低时。本文提出的SPH-DEM模型具有通用性，适用于不同叶片、固体颗粒密度和尺寸以及液体粘结剂的颗粒混合过程的虚拟实验，因此可以加快混凝土材料和颗粒复合材料的设计与开发。
