Direct numerical simulation of particle mixing in dispersed gas-liquid-solid flows using a combined volume of fluid and discrete particle approach

In this paper a hybrid model is presented for the numerical simulation of gas-liquid-solid flows using a combined Volume Of Fluid (VOF) and Discrete Particle (DP) approach applied for respectively dispersed gas bubbles and solid particles present in the continuous liquid phase. The hard sphere DP model, originally developed by Hoomans et al. (1996) for dense gas-solid systems, has been extended to account for all additional forces acting on particles suspended in a viscous liquid and has been combined with the VOF model presented recently by van Sint Annaland et al. (2005) for complex free surface flows. In this paper the physical foundation of the combined VOF-DP model will be presented together with illustrative computational results highlighting the capabilities of this hybrid model. The effect of bubble-induced particle mixing has been studied focusing on the effect of the volumetric particle concentration. In addition particle mixing was studied in systems with coalescing bubbles.