Development and application of innovative discrete element modelling for industrial systems

Due to remarkable improvement in computer hardware capability, numerical simulations are  tried to be applied to actually industrial systems. The discrete element method (DEM) has been frequently employed in numerical simulations for the powder processes. In my group, several innovative models have been developed to perform DEM simulations in industrial powder processes. In this paper, overview of the innovative methods and the industrial applications are described.

Recently, the sign distance functions SDF has been developed to create wall boundaries for the DEM by scalar fields. The SDF is composed with sign and distance, and is saved spatially with equivalent interval in the calculation domain. The sign becomes positive inside of the calculation domain and vice versa. The SDF makes it possible to create a complex shape wall boundary easily without generating meshes. Adequacy of the SDF has been shown through validation tests in a twin-screw kneader, a ribbon mixer and powder die-filling.

Very recently, combination of the SDF and the immersed boundary method (IBM) has been developed for simulations of multi-phase flows including solid particles. The SDF and the IBM are applied to wall boundary in the DEM and the CFD, respectively. In the combinational boundary model, the local volume for the IBM is estimated based upon the SDF. This combinational boundary model makes it feasible to create an arbitrary shape wall with simple algorithm even using staggered grids. Besides, this model is available for a multi-phase flow in a moving wall system. Adequacy of the combinational boundary model is designated in die-filling and a fluidized bed. Hence, the SDF and the combinational boundary model of the SDF and IBM is shown to be useful for a granular flow and a multi-phase flow in an industrial system.

Dr Mikio Sakai is currently Associate Professor in the Resilience Engineering Research Center in The University of Tokyo. He earned his Ph.D. degree from The University of Tokyo in 2006. Then, he became Assistant Professor in 2007 and Associate Professor in 2008. He has been Visiting Reader at Imperial College London since 2016. He extensively studies modeling of granular flows, multi-phase flows and the heat transfer, and the parallel computation techniques. He is a world-leading professor in computational granular dynamics, and hence has delivered lots of invited lectures in conferences. He holds important posts in powder technology community such as Director of Society of Powder Technology of Japan and Head of Simulation & Modeling Division in Association of Powder Process Industry and Engineering, JAPAN. At present, he is Associate Editor of Chemical Engineering Science and Editor of Granular Matter.