(45b) Optimum Cell Condition for Fast Contact Detection in the Algorithm of Dem and Its Application to Large-Computing

The granular materials are used in many industry fields, and their flows or behaviours in the processes are very important because their forms and characteristics are changed continuously. Discrete Element Method (DEM) is one of the most popular simulation methods for the analysis of solid particle behaviour, and many processes have been modelled. However, the systems in the industries are large, and there are a huge number of particles. Therefore, the speed up of calculation and large-computing of DEM are needed. The objective of this paper is to find out the optimum cell size for fast contact detection in the algorithm of DEM to improve the calculation speed. The computing time of contact detection was measured to investigate the effect of cell size by using a cubic box, which contains about 500,000 particles. The contact detection was inefficient when too fine grid cell or large one was used, the optimum cell size was given around 1.5~2.0 times of particle radius. The theoretical formula to find the optimum cell size was proposed by considering the effects of the number of searched cells and contact checks. A significant correlation between the computing time of DEM work and the theoretical equation was seen, irrespective of volume fraction. Furthermore, it was found that the optimum cell size was the size, which each cell has about 0.7~1.0 particles in it, and this result was applied to conditions of particles having distributed size. Therefore, the calculation speed of DEM would be improved by using the optimum cell size, and large computing of DEM would be possible.