Comparisons of TFM and DEM-CFD simulation analyses on the influence mechanism of electrostatics on single bubble in gas-solid fluidized bed
Electrostatics occurs in the gas-solid fluidization processes, which influences the hydrodynamics of gas-solid flow. Numerical simulation has been applied to study the electrostatic phenomena in gas-solid flow in recent years, including Eulerian-Eulerian and Eulerian-Lagrangian approaches. However, few detailed research has investigated the influence mechanism of electrostatics on the hydrodynamics of gas-solid flow, while no study has focused on comparisons of Eulerian-Eulerian and Eulerian-Lagrangian approaches. In this work, both Two-Fluid Model (TFM) and Discrete Element Method-Computational Fluid Dynamics (DEM-CFD) are implemented to analyze the reason of single bubble deformation in charged system. The analyses are carried out from the magnitude and direction of the electrostatic force acting on the particles. For a more comprehensive study of the influence mechanism, mono-charged system and bipolar-charged system are simulated respectively. This paper compares the Eulerian-Eulerian and Eulerian-Lagrangian approaches and elaborates on their calculation principles respectively. The advantages and disadvantages of these two approaches are also analyzed in this work. During the compilation of Two-Fluid Model, a scalar equation describing the electric potential gradient is derived by Maxwell’s equations and the Bruggeman’s equation. The direction of the electrostatic force is obtained by solving the electric potential gradient. And the magnitude of electrostatic force is described by Lorentz force equation. In the simulation applying DEM-CFD, the magnitude and direction of the electrostatic force acting on the single particles are obtained by solving Coulomb’s law directly. Both approaches have their pros and cons. The basic mathematical representations of these two approaches are the same, while the simulation results differ significantly, which is due to the respective characteristics.
Keywords: Electrostatics, Electrostatic force, Discrete element method, Two fluid model, Computational fluid dynamics,