Modeling and numerical study of particle-bubble-liquid flows using a front-tracking and discrete-element method

Particle-bubble-liquid flows widely exist in industrial processes, such as fluidized beds, flotation cells, and bubble column reactors, but the high-fidelity simulation of these flows is a great challenge. This paper developed a dynamic model for this three-phase system using a front-tracking and discrete-element method, where the behaviors of collision, attachment, and detachment between the particles and bubbles are included. The convergence and accuracy of this model were validated, and then the model was applied to simulate the transport behaviors of particle-bubble-liquid flows. The collision and attachment probabilities and the effects of particle size and properties on the collision, attachment, and flow behaviors were numerically investigated. The particle-bubble interaction simulations show that the collision probability and contact time increase with the increase of the size ratio of particle to bubble; hydrophilic particles can promote the bubble rising speed and even faster than that in the pure liquid; the attachment behavior greatly impedes the bubble rising but enhances the particle transport intensity. The bubbling simulations show that the wake of the rising bubble can induce the following bubble to move along a wave-like trajectory; the particles driven by a higher bubbling frequency present a higher lifting height and a stronger dispersion effect.