Assessing the capability of continuum and discrete particle methods to simulate gas-solids flow using DNS predictions as a benchmark

• Published in: Powder technology 2017-11, Vol.321 (C), p.301-309
• Main Authors: Lu, Liqiang, Liu, Xiaowen, Li, Tingwen, Wang, Limin, Ge, Wei, Benyahia, Sofiane
• Format: Article
• Language: English
• Subjects: Aspect ratio; Benchmarks; Clusters; Computational fluid dynamics; Computer applications; Computer simulation; Current distribution; Direct numerical simulation; Discrete element method; Domain names; Drag; Drag model; ENGINEERING; Flow velocity; Fluid dynamics; Fluidized bed; Gas flow; Mathematical models; MATHEMATICS AND COMPUTING; Particle methods (mathematics); Particle size distribution; Predictions; Size distribution; Slip; Slip velocity; Solids; Solids flow; Three dimensional flow; Two fluid models; Two-fluid model
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2017.08.034

Gas–solids flow in a three-dimension periodic domain was numerically investigated by direct numerical simulation (DNS), computational fluid dynamic-discrete element method (CFD-DEM) and two-fluid model (TFM). DNS data obtained by finely resolving the flow around every particle are used as a benchmark to assess the validity of coarser DEM and TFM approaches. The CFD-DEM predicts the correct cluster size distribution and under-predicts the macro-scale slip velocity even with a grid size as small as twice the particle diameter. The TFM approach predicts larger cluster size and lower slip velocity with a homogeneous drag correlation. Although the slip velocity can be matched by a simple modification to the drag model, the predicted voidage distribution is still different from DNS: Both CFD-DEM and TFM over-predict the fraction of particles in dense regions and under-predict the fraction of particles in regions of intermediate void fractions. Also, the cluster aspect ratio of DNS is smaller than CFD-DEM and TFM. Since a simple correction to the drag model can predict a correct slip velocity, it is hopeful that drag corrections based on more elaborate theories that consider voidage gradient and particle fluctuations may be able to improve the current predictions of cluster distribution. [Display omitted] •Validity of CFD-DEM and TFM are assessed using DNS data.•CFD-DEM predicts correct cluster size and smaller slip velocity.•TFM predicts larger cluster size and lower slip velocity.•Both CFD-DEM and TFM predict larger cluster aspect ratio.•A more accurate drag model is needed to accurately simulate gas-solids flow.