(116h) Numerical Simulation of Gas-Liquid Flow in a Flat Bubble Column Using the Lattice-Boltzmann Scheme

Bubble columns are widely used in the chemical and pharmaceutical industry to produce a variety of products. It has been known that these devices are characterized by a high degree of unsteadiness and complexity¹. Thus, a detailed understanding of the liquid-phase flow field and the bubble dispersion pattern is crucial in the design and scale-up of bubble columns.

By using computational fluid dynamics (CFD) modeling it is possible to gain insight into the details of flow and mixing in these multiphase systems. Although significant efforts have been invested in the field of bubble column simulation, challenges still remain. For example, fully resolved 3D simulations of commercial-scale bubble columns are prohibitively expensive for conventional CFD models. Therefore, we focus on developing a reliable computational tool with high efficiency in parallel computation.

In this work we studied gas-liquid flow in a laboratory-scale bubble column (the so-called Becker case²) by means of Large Eddy Simulation (LES) combined with Lagrangian particle tracking with two-way coupling. This approach is known as the Eulerian-Lagrangian (EL) method. The same lattice-Boltzmann scheme as employed by Derksen³ is extended for discretizing the Navier-Stokes equations. To the best of the author's knowledge, this is the first application of the lattice-Boltzmann scheme with Lagrangian particle tracking to simulate bubbly flows. We have chosen this scheme because of its outstanding computational efficiency especially on parallel computer platforms³. Our work also includes an efficient scheme for checking the distance between the particles and the cells⁴. Excellent agreement with experimental data² for the mean velocity field as well as the transient bubble dispersion patterns is obtained. Also, we show that our code is significantly more efficient in terms of computation time and speed-up compared to conventional CFD codes.

References

(1) Hu G, Celik I. Eulerian-Lagrangian based Large-Eddy Simulation of a Partially Aerated Flat Bubble Column. Chemical Engineering Science 2008;63:253-271.

(2) Becker S, De Bie H, Sweeney J. Dynamic Flow Behaviour in Bubble Columns and Loop Reactors: Part II. Comparison of Detailed Experiments and Flow Simulations. Chemical Engineering Science 1994;49:5747-5762.

(3) Derksen JJ, Van den Akker HEA. Large Eddy Simulations on the Flow Driven by a Rushton Turbine. AIChE Journal 1999;45:209-221.

(4) Radl S, Khinast JG. Multiphase Flow and Mixing in Dilute Bubble Swarms. Submitted to AIChE Journal.