Experimental and numerical studies of the hydrodynamics in a bubble column

The hydrodynamics in a bubble column of 140 mm diameter and a height of 650 mm was analysed using a phase-Doppler anemometer (PDA). In order to allow the application of PDA, the bubble column was aerated with relatively fine bubbles with a size spectrum between about 0.3 and 1.5 mm. The gas hold-up was varied in the range between 0.5 and 3%. The measurement of the liquid velocities in the bubble swarm was done by adding fluorescing seed particles. Moreover, the Euler/Lagrange approach was extended to allow time-dependent calculations of the flow evolving in a bubble column based on the Reynolds-averaged Navier-Stokes equations together with the k-epsilon turbulence model which was extended to account for turbulence modification by the bubbles. The coupling between the phases was considered through momentum source terms and source terms in the k- and epsilon-equation which also include the effect of wake-generated turbulence. The bubble motion was calculated by solving an equation of motion taking into account drag force, added mass, buoyancy and gravity, and the transverse lift force. In order to identify the relative importance of the different physical phenomena involved in the model, a detailed parametric study was performed and the numerical results were compared with the measurements for validation. (C) 1999 Elsevier Science Ltd. All rights reserved.