Numerical simulation of gas–liquid–solid flows using a combined front tracking and discrete particle method

In this paper a hybrid model is presented for the numerical simulation of gas–liquid–solid flows using a combined front tracking (FT) 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. Chemical Engineering Science 51, 99–108] 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 FT model presented recently by Deen et al. [2004a. CD-ROM Proceedings of Fifth International Conference on Multiphase Flow, ICMF’04, Yokohama, Japan, May 30–June 4, 2004; 2004b. Chemical Engineering Science 59, 1853–1861] for complex free surface flows. In this paper, the physical foundation of the combined FT-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 the retarding effect (drag modification) on the bubble rise velocity due to the presence of the suspended solid particles has been quantified.