Die filling is an important manufacturing process that is widely involved in material science and technology in chemical engineering. Application of numerical technologies is desired in optimizing a die filling process. The Discrete Element Method (DEM) is widely used to simulate granular flows in die filling. However, the existing DEM has a problem regarding the computation of air flow in a moving shoe system, even though the DEM is coupled with computational fluid dynamics (CFD). This is because that the simulation of a gas-solid flow with a moving boundary requires an extremely complex algorithm. In order to solve this problem, The Advanced DEM-CFD method is proposed to calculate granular particles interacting with air meanwhile during the whole die filling process. In the Advanced DEM-CFD method, a compact algorithm is employed to simulate a gas-solid flow in a moving boundary system, where wall boundary is modeled by Signed Distance Function and Immersed Boundary Method for solid phase and fluid phase. Validation tests are performed to show the adequacy of the Advanced DEM-CFD method. The results show that the simulations well agree with the experiments, and hence our numerical approach is adequate to reproduce actual die filling processes.

模具填充是重要的制造过程，广泛涉及化学工程的材料科学和技术。在优化模具填充过程中需要数值技术的应用。离散元素方法（DEM）被广泛用于模拟模具填充过程中的颗粒流动。但是，即使DEM与计算流体动力学（CFD）耦合，现有的DEM在动靴系统中的气流计算也存在问题。这是因为模拟具有移动边界的气固流需要非常复杂的算法。为了解决这一问题，提出了一种先进的DEM-CFD方法来计算在整个模具填充过程中同时与空气相互作用的颗粒。在高级DEM-CFD方法中，在运动边界系统中，采用紧凑算法模拟气固两相流，其中壁面边界通过符号距离函数和浸入边界法对固相和流体相进行建模。执行验证测试以显示高级DEM-CFD方法的适当性。结果表明，仿真与实验非常吻合，因此我们的数值方法足以重现实际的模具填充过程。