Applicability of the standard k-ε turbulence model to the dynamic simulation of bubble columns:: Part I.: Detailed numerical simulations

Detailed simulation results for the test case of a locally aerated hat bubble column for laminar and turbulent models of Euler-Euler type in two and three dimensions are presented for different space resolutions. The flow structure observed in the experiment has an instationary turbulent character. If the 2D laminar model is applied for calculations the dynamic character of the flow field can be resolved, but the simulation results depend strongly on the space resolution used. If the 2D k-epsilon turbulence model is used instead, the grid independent solution can be achieved on a relatively coarse grid, but the dynamic nature of the flow is not reproduced in the simulation. Only if the 3D turbulent model is used, the simulation results show a good agreement with experiments. This means, that the three-dimensional effects which are neglected in the 2D simulation have a strong influence on the numerical solution. Further, the influence of the discretization on the accuracy of the solution is discussed, and a comparison between results obtained with 2D Euler-Euler and Euler-Lagrange models is presented. (C) 1999 Elsevier Science Ltd. All rights reserved.