Development of a large scale model of discrete element method

离散单元法（DEM）被广泛用于计算与固体颗粒行为有关的复杂现象。另一方面，DEM由于计算成本过高，不能应用于大规模系统。事实上，通过使用最新的PC，计算出的粒子数变成了几十万。也就是说，DEM不能应用于处理超过十亿颗粒的工业系统。因此，现在需要开发DEM的大规模模型。为了解决这个问题，我们已经开发了一个粗颗粒模型的DEM，其中大尺寸的建模颗粒代表一组原始颗粒。将粗粒模型应用于典型的气固和固液两相流动。在过去的研究中，粗晶模型的充分性是通过数值算例来证明的。粗晶粒模型的验证是实际应用所必需的。在目前的研究中，我们显示的粗晶粒模型的有效性测试。

The Discrete Element Method(DEM) is widely used to figure out the complicated phenomena related to solid particle behavior. On the other hand, the DEM could not be applied to large scale systems because of the excessive calculation cost. In fact, the number of the calculated particles became a few hundred thousand by using a latest PC. Namely, the DEM could not be applied to industrial systems, where over billion particles were dealt with. Accordingly, development of a large-scale model of the DEM is desired now. To solve this problem, we have developed a coarse grain model of the DEM, where large-sized modeled particle represents a group of original particles. The coarse grain model was applied to typical gas-solid and solid-liquid flows. In the past studies, adequacy of the coarse grain model was shown by numerical examples. Validation of the coarse grain model was required for the practical usage. In the present study, we show the adequacy of the coarse grain model by the validation tests.