Transient three-dimensional numerical analyses of shallow bubble column

Two-phase flow in a shallow bubble column (radius equal to the height) was studied. The primary objectives were to study both the effect of the: free surface on the whole flow mode and the three-dimensionality in the whole do main. Air bubbles were injected through a central porous bottom wall of a c ylindrical water tank. The flow pattern was visualized with dispersed alumi nium particles. The velocity of the liquid phase was measured with a laser- Doppler velocimeter. The system was numerically analysed with a dispersed f low model. The inertial terms in the momentum equations were approximated b y the QUICK scheme. Two models for the top surface were employed, namely ei ther slip or non-slip conditions. The computed result with non-slip conditi ons agreed fairly well with the experimental result. A three-dimensional ca lculation was carried out with non-slip conditions for the top water surfac e. The calculated flow pattern agreed better with the experimental pattern than the two-dimensional calculation. In the results, two spiral vortices m oving vertically were found outside the central upward flow. The flow was s trongly three-dimensional, even though the vessel was shallow. (C) 2000 Els evier Science S.A. All rights reserved.