Three-dimensional numerical simulation of rising bubbles in the presence of cylindrical obstacles, using lattice Boltzmann method

Atypical process in many industrial applications is rising bubble dynamic in viscous liquids like two-phase reactors. Examining the physical behavior of bubbles may improve the understanding of systems regarding design and operation. This study focused on the splitting of bubbles resulting from their impact on solid obstacles, Fragmentation of the bubbles appears in many applications such as lab on a chip in small scale or slug bubbly flow moving upward in a tube in large scales. Using a new index-function model in Lattice Boltzmann technique proposed by "He", we simulated the deformation and motion of a bubble in different regimes, through which, we accurately captured a sharp interface between the two phases. We extended the aforementioned technique from 2D-to 3D modelling of buoyancy-driven motion of a single bubble in quiescent viscous liquid. It was demonstrated that there is a reasonable agreement in terms of terminal rising velocity as well as bubble shape. This was found by comparing it with other available experimental and numerical results in different regimes through varying the two non-dimensional numbers (Eotvos and Morton) to characterize the fluid regime behind the rising bubble. In addition, by applying Bounce-Back no slip boundary condition to the surface area of the tubes with circular cross sections, we simulated the impact of the bubble during, its upward motion. Changing the distance between the tubes and their corresponding diameters causes different shapes in the bubbles. Our simulation demonstrated that the 3D model based on index-function model of LBM is a suitable tool for 3D numerical simulation of rising bubbles in the presence of obstacles. (C) 2017 Elsevier B.V. All rights reserved.