Two fluid model LES of a bubble column

The hydrodynamics of a rectangular bubble column operating in the dispersed bubbly regime has been numerically investigated using a two-fluid model Large Eddy Simulation (LES). Experimental data was obtained to validate the numerical model. LES computational fluid dynamic calculations of the transient flow for the bubble column were performed to account for the turbulence in the liquid phase. The computational mesh is of the same scale as the bubble size. The sub-grid scale Reynolds stresses were calculated using the Smagorinsky model. Furthermore, the effect of the bubbles on the turbulence in the continuous phase was modeled using Sato’s eddy viscosity model for bubble-induced turbulence. LES facilitates the direct numerical resolution of length scales that play an important role in the transport of bubbles, avoiding the need for constitutive models like the turbulent diffusion force to account for diffusion of the gas phase under the influence of the large eddies. Mean quantities, in particular the void fraction and the average velocity of the bubbles, were computed by averaging over a time period that was longer than the dynamic time scales of the turbulence. A systematic analysis of the effect of the interfacial momentum transfer terms on these quantities has been conducted. The bubble column was locally aerated using a sparger located in the center of the bottom plate. The model was validated with experimental data (Reddy Vanga, 2004) obtained using wire-mesh tomography measurements for void fraction and bubble size distributions. The experiments were performed for various aspect ratios (height of water column to width ratio) and superficial gas velocities.