(297f) Euler-Lagrange Modeling of Turbulent Bubbly Flows with Coalescence and Breakup

Euler-Lagrange simulations of turbulent bubbly flows with significant gas holdup are extremely demanding. This is because a large number of bubbles are present in industrial-scale reactors where coalescence and breakup typically need to be taken into account. Consequently, bubble-bubble collisions must be simulated, which requires an immense computational effort if it is done directly, i.e., by detecting each and every collisions. Clearly, using currently available methods, Euler-Lagrange simulations of industrial-scale bubble reactors are not feasible.

We significantly extended our previously used models (refer to Radl et al.² as well as Sungkorn et al.³) by also taking into account bubble coalescence and breakup phenomena. The continuous phase (i.e., the liquid) is simulated using the lattice Boltzmann (LB) scheme developed by Derksen and Van den Akker.¹ The effect of the fluid fluctuation along the bubble trajectories is modeled using the Langevin equation. Bubble-bubble collisions as well as coalescences are described based on a stochastic inter-particle collision model. Also, the breakup of bubbles is considered using a model based on the local size of turbulent eddies.

Simulations of gas-liquid flow in a stirred tank have been performed. The simulations provide detailed insight for the liquid flow field as well as the gas dispersion pattern. The accuracy of the simulations is demonstrated by comparing the predictions with experimental data. In addition, the excellent speedup on a parallel computing platform demonstrates the potential of the present modeling technique for simulations of industrial-scale reactors.

References

1. Derksen JJ, Van den Akker HEA. Large eddy simulations on the flow driven by a Rushton turbine. AIChE Journal. 1999;45:209-221.

2. Radl S, Suzzi D, Khinast JG. High Performance Simulation of Bubbly Flows: Pushing the Limit by Using Conventional CFD and LBGK. Proceeding of CSIRO Multiscale Modeling Symposium 2009.

3. Sungkorn R, Derksen JJ, Khinast JG. Modeling of turbulent gas-liquid bubbly flows. To be submitted to AIChE Journal.