Effective particle diameters for simulating fluidization of non-spherical particles: CFD-DEM models vs. MRI measurements

Computational fluid dynamics—discrete element method (CFD-DEM) simulations were conducted and compared with magnetic resonance imaging (MRI) measurements (Boyce, Rice, and Ozel et al., Phys Rev Fluids. 2016;1(7):074201) of gas and particle motion in a three-dimensional cylindrical bubbling fluidized bed. Experimental particles had a kidney-bean-like shape, while particles were simulated as being spherical; to account for non-sphericity, “effective” diameters were introduced to calculate drag and void fraction, such that the void fraction at minimum fluidization (εmf) and the minimum fluidization velocity (Umf) in the simulations matched experimental values. With the use of effective diameters, similar bubbling patterns were seen in experiments and simulations, and the simulation predictions matched measurements of average gas and particle velocity in bubbling and emulsion regions low in the bed. Simulations which did not employ effective diameters were found to produce vastly different bubbling patterns when different drag laws were used. Both MRI results and CFD-DEM simulations agreed with classic analytical theory for gas flow and bubble motion in bubbling fluidized beds.