A novel two-grid formulation for fluid–particle systems using the discrete element method

• Published in: Powder technology Vol. 246; pp. 601 - 616
• Main Authors: Deb, Surya, Tafti, Danesh K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2013; Elsevier
• Subjects: Applied sciences; Chemical engineering; Computation; Discrete element modeling; Exact sciences and technology; Fluid mechanics; Fluidization; fluidized beds; friction; Heat and mass transfer. Packings, plates; heat transfer coefficient; Hydrodynamics of contact apparatus; Miscellaneous; Multiphase flow; Particulate processes; Solid-solid systems; turbulent flow; Fluid mechanics; Particulate processes; Discrete element modeling; Fluidization; Multiphase flow; Computation; Cartography; Turbulence; Computational fluid dynamics; Interphase; Void fraction; Discrete element method; Heat transfer coefficient; Modeling; Friction; Heat transfer; Fluidized bed
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2013.06.014

Discrete element modeling (DEM) coupled with computational fluid dynamics (CFD) provides an excellent platform to analyze fluid–particle systems. In all previous work, the fluid and particle systems are solved on a single grid. Contradictory requirements posed by resolution of fine scale fluid features such as turbulence, friction and heat transfer coefficient at immersed surfaces, and the resolution of important geometrical features, versus the necessity to maintain smoothness in particle solid fraction distribution on the chosen grid, often make single grid calculations untenable. To overcome this challenge, we have developed a novel two-grid technique in which a coarser particle grid is mapped on to a fine fluid grid. The technique uses suitable mappings to transfer fluid field variables from fluid-to-particle grid, and interphase transfer terms and void fractions from particle-to-fluid grid. The method is applied to a jetting fluidized bed of 750μm particles with a characteristic jet width of 1.6mm. Results in the form of time-averaged void fractions and solid-velocity for two inlet jet velocities with single and multiple jets are compared to experiments. The results agree reasonably well with the experiments validating the two-grid approach for cases where single grid DEM–CFD would have been difficult to apply. [Display omitted] •Two-grid formulation is necessary when key geometrical features are of same scale as particle diameter.•A novel formulation using separate grids for fluid and particles is formulated.•Validations with experiments have been performed.•Overall the trends predicted by the two-grid method agree well with experiments.