Applicability of the standard k-epsilon turbulence model to the dynamic simulation of bubble columns. Part II: Comparison of detailed experiments andflow simulations

Gas-liquid bubble-flow was studied in a flat bubble column with rectangular cross-section. The bubble column was locally aerated through a frit sparge r, located in the central part of the bottom plate. The experimental techni ques used comprise photographic documentation of the bubble distribution as well as LDA measurements of the liquid velocity. The influence of the liqu id level (aspect ratio) in the bubble column and of the gas through-put on the hydrodynamic behaviour of the column has been investigated. Al aspect r atio of 1 steady state flow was observed with one circulation cell spread o ver the full width of the column. This differs from the flow behaviour in a uniformly aerated flat bubble column, reported by Chen, Jamialahmadi and L i (Chemical Engineering Research and Development 67 (1989) 203-207), who ob served an essentially symmetric flow field with two stationary circulation cells. At aspect ratios of 2 and 3 the two-phase flow has a transient chara cter with two staggered rows of vortices moving downwards in a periodic way . The long-time averaged liquid velocities obtained from the LDA measuremen ts showed a symmetrical flow field, which is referred to in the literature as the "Gulf-stream" or "cooling-tower" pattern. The experimental results w ere compared with numerical simulations based upon the dynamic turbulent th ree-dimensional two-phase Euler-Euler model presented in Part I(Sokolichin and Eigenberger, Chemical Engineering. Since (1999) in press). (Good qualit ative and quantitative agreement was found for the steady state as well as for the transient case. (C) 1999 Elsevier Science Ltd. All rights reserved.