Modeling, simulation & analysis of the flow in a bubble column

Abstract

Understanding multiphase flows in bubble columns is crucial for various engineering applications. This study models a rectangular bubble column of laminar flow with a height of 2 meters and a width of 0.5 meters, where the inlet velocity of air is set at 3.3 mm/s. The simulations were done on Ansys Fluent using the mixture model, Volume of Fluid model and Eulerian model for two different numerical schemes, namely the first order upwind and the quadratic upstream interpolation for convective kinetics schemes. The mesh independence study demonstrated that in 2D simulations, mesh independence was achieved exclusively using the Eulerian model indicating that the Eulerian model is the most effective for simulating bubbly flow. Furthermore, when applying finer meshes in 3D simulations, the results closely aligned with the 2D simulations, supporting the validity of a 2D approach in the case of such flat bubble column. Additionally, finer meshes show thinner bubble swarms, particularly at the inlet. This study also investigated the impact of various parameters on bubble flow dynamics. It was found that the air inlet velocity, bubble sizes, and the properties of the working fluids significantly influenced the results. Specifically, as the air inlet velocity increased, the air volume fraction also increased. Conversely, increasing bubble sizes led to a decrease in both the air volume fraction and the water velocity, due to a reduced surface area to volume ratio. Moreover, changes in the working fluids showed that viscosity and density greatly affect the bubbly flow within the bubble column, highlighting the sensitivity of the system to these fluid properties.