Simulation bubbling/turbulent

Lathouwers, D., Modelling and simulation of turbulent bubbly flow , Ph.D. Thesis, Delft University of Technology, Delft, Netherlands (1999). 

Ranade, V.V. (1993b), Numerical simulation of turbulent flow in bubble column reactors, AIChE Symposium Series no. 293, 89, 61-71. 

Antal SP, Lahey Jr RT, Al-Dahhan MH (2004) Simulating Churn-Turbulent Flows in a Bubble Column using a Three Field, Two-Fluid Model. Paper presented at the 5th International Conference on Multiphase Flow, ICMF 04, Yokohama, Japan, May 30-June 4, Paper No. 182... 

Lathouwers D (1999) Modeling and simulation of turbulent bubbly flow. PhD thesis, the Technical University in Delft, the Netherlands... 

Ekambra etal. [21] compared the results from ID, 2D, and 3D simulations of a bubble column with experimental results. They obtained similar results for holdup and axial velocity, while eddy viscosity, Reynolds stresses, and energy dissipation were very different in the three simulations as shown in Figure 15.7. This example also illustrates the importance of selecting the right variables for model vahdation. A 2D model will yield good results for velocity but will predict all variables based on turbulent characteristics poorly. 

In system 1, the 3-D dynamic bubbling phenomena in a gas liquid bubble column and a gas liquid solid fluidized bed are simulated using the level-set method coupled with an SGS model for liquid turbulence. The computational scheme in this study captures the complex topological changes related to the bubble deformation, coalescence, and breakup in bubbling flows. In system 2, the hydrodynamics and heat-transfer phenomena of liquid droplets impacting upon a hot flat surface and particle are analyzed based on 3-D level-set method and IBM with consideration of the film-boiling behavior. The heat transfers in... 

CFD might provide a way of elucidating all these spatial variations in flow conditions, in species concentrations, in bubble drop and particle sizes, and in chemical reaction rates, provided that such computational simulations are already capable of reliably reproducing the details of turbulent flows and their dynamic effects on the processes of interest. This Chapter reviews the state of the art in simulating the details of turbulent flows and turbulent mixing processes, mainly in stirred vessels. To this end, the topics of turbulence and CFD both need a separate introduction. 

Just like in the context of simulating solids suspension, one may wonder whether much may be expected from just sticking to the two-fluid approach combined with population balances. A better way ahead might rather be to combine population balances with LES, while proper relations for the various kernels used for describing coalescence and break-up processes could be determined from DNS of periodic boxes comprising a certain number of bubbles (or drops). The latter simulations would serve to study the detailed response of bubbles or drops to the ambient turbulent flow. 

Krishna R, Urseanu MI, van Baten JM, Ellenberger J. Influence of scale on the hydrodynamics of bubble columns operating in the chum-turbulent regime experiments vs. Eulerian simulations. Chem Eng Sci 1999 54 4903 -911. 

In the process under study here, where S02 oxidation is the limiting half reaction, the electrolyte flow rates are controlled by volumetric pumps to ensure forced convection. Moreover, both the anode and cathode compartments are provided with a plastic mesh turbulence promoter. The flow is therefore assumed fully turbulent and a uniform velocity profile is assumed at the inlet. However, for simplification, these devices are not represented in the simulation domain. Although the turbulence promoter should actually influence the bubble population, no reference has been found on its effects. 

The bubbles occurring in the present electrochemical system are small enough to fulfil the criterion of Stokes flow. Thus, turbulent wakes arising behind bubbles can be neglected [26], Furthermore, we consider all bubbles in the present simulations as small, non-deformable and rigid spheres. This hypothesis holds for bubbles of low Eotvos numbers Eo ... 

The recent progress in experimental techniques and applications of DNS and LES for turbulent multiphase flows may lead to new insights necessary to develop better computational models to simulate dispersed multiphase flows with wide particle size distribution in turbulent regimes. Until then, the simulations of such complex turbulent multiphase flow processes have to be accompanied by careful validation (to assess errors due to modeling) and error estimation (due to numerical issues) exercise. Applications of these models to simulate multiphase stirred reactors, bubble column reactors and fluidized bed reactors, are discussed in Part IV of this book. 

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