Eulerian computation, compared

This study investigates the hydrodynamic behaviour of an aimular bubble column reactor with continuous liquid and gas flow using an Eulerian-Eulerian computational fluid dynamics approach. The residence time distribution is completed using a numerical scalar technique which compares favourably to the corresponding experimental data. It is shown that liquid mixing performance and residence time are strong functions of flowrate and direction. 

Discrete particle modeling (DPM) is an advanced computational technique for particulate systems (in this case, fluidized beds) that has already been presented in Chapter 7 of Volume 3, Modem Drying TechnoU. DPM combines continuous (Eulerian) CFD for the gas phase with a discrete (Lagrangian) consideration of the particle phase by means of a discrete element method (DEM), and is therefore often also denoted as DEM-CFD. Its appHcation enables the resolution of not only interactions between the gas and the particle phase, but also of particle-particle and particle-wall interactions, in the sense of a four-way coupling (compare also with Chapter 5 in Volume 1, Modem Drying Technology). 

By extrapolation of the computed autocorrelation coefficient to zero time the square of the llagrangian fluctuating velocity can be obtained. The square root of this quantity can then be compared to the Eulerian rms velocity for the same column compartment. The two velocities should be equal in case of homogeneous turbulence. Devanathan (1991) shows that this is not the case in bubble columns but that homogeneous turbulence is approached at the highest gas velocities in the largest diameter column. 

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