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Partic. vol. 34 pp. 61-69 (October 2017)
doi: 10.1016/j.partic.2016.12.002

Effects of grid size on predictions of bed expansion in bubbling fluidized beds of Geldart B particles: A generalized rule for a grid-independent solution of TFM simulations

M. Helal Uddin, Charles J. Coronella*

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    • Particle has small effect on dimensionless grid size. • Excessively resolved simulations showed physically unrealistic bed expansion. • Small particles are carried with the gas streamline in for coarse grid simulations. • Grid size of 18 particle diameters is sufficient for Geldart B particle simulation by TFM.


Numerical simulations of gas–solid fluidized beds based on the kinetic theory of granular flow exhibit a significant dependence on domain discretization. Bubble formation, bubble size and shape all vary greatly with the discretization, and the use of an inappropriate scale resolution leads to inaccurate predictions of fluidization hydrodynamics. In this study, grid-independent solutions of the two fluid model were examined by comparing the bed expansions obtained from numerical simulations with experimental results and empirical predictions, based on bubbling fluidized beds of Geldart B particles. Grid independence was achieved with a grid resolution equal to 18 times the particle diameter. The simulation results were compared with previously published data for verification purposes. The results of this work should provide a guideline for choosing the appropriate grid size and thereby minimize the time and expense associated with large simulations.

Graphical abstract


Mesh effect; Hydrodynamics; Computational fluid dynamics; Euler–Euler method; MFIX