Comparison of Two-Fluid Model Simulations of Freely Bubbling Three-Dimensional Gas-Fluidized Beds with Magnetic Resonance Imaging Results

Abstract

Two-fluid model (TFM) simulation predictions of bubble and particle dynamics in a 3D cylindrical fluidized bed are compared with magnetic resonance imaging (MRI) measurements from a prior study across a range of gas velocities, particle sizes, and bed heights. TFM simulations generally predict the number of bubbles and bubble diameters seen as a function of vertical position of the bubbles in the bed well; however, simulations generally predict particle speeds lower than those measured experimentally. The drag model and particle stress model used in the simulations were varied and found to have an insignificant effect on predictions of bubble dynamics but a significant effect on predictions of particle velocity distribution. Overall, this study demonstrates the importance of challenging model predictions of both particle and bubble dynamics and the ability of the prior MRI results to evaluate the accuracy of submodels, such as drag and particle stress closure relationships.

Contact-Based Method to Evaluate Mixing in Multicomponent Experiments and Simulations

“…Two-fluid modeling (TFM) has been widely used in the literature, ,− simulating gas and particles as interpenetrating continua using computational fluid dynamics (CFD), utilizing constitutive relationships to model an effective stress of the particle phase and coupling gas and solid flow using a drag law. The governing equations and constitutive relationships used for TFM are shown below.…”

Efficiency Analysis of the Discrete Element Method Model in Gas‐Fluidized Beds

“…The computational fluid dynamics (CFD) predictions generally agreed with measurements in many studies, but it is inevitable that there will be differences between simulations and experiments in some cases as well [6,7]. A number of critical submodels have been evaluated in order to improve CFD predictions [8][9][10].…”

Bubble-Based EMMS Drag Model for Particle Segregation Simulation with a Continuous Size Distribution

“…For the 3D bubbling fluidized bed, the cut-cell technique in MFIX can be used to fit the cylindrical geometry by unstructured meshes . Square grids were used in the central area and wedge-shaped grids were used in the near wall area.…”

“…t g g g g g g g g g g g g s granular temperature equation For the 3D bubbling fluidized bed, the cut-cell technique in MFIX can be used to fit the cylindrical geometry by unstructured meshes. 52 Square grids were used in the central area and wedge-shaped grids were used in the near wall area. Three grid sizes (grid 1: ΔX = ΔY = 2.82 mm, ΔZ = 3.1 mm; grid 2: ΔX = ΔY = 1.88 mm, ΔZ = 2.07 mm; grid 3: ΔX = ΔY = 1.41 mm, ΔZ = 1.55 mm) were chosen to test the meshindependence of simulating the segregation processes of polydisperse particles.…”