Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

2 Publications
Validation of models for bubble forces
Lucas, D.; Krepper, E.; Prasser, H.-M.;
Closure laws are needed for the qualification of CFD codes for two-phase flows. In case of bubbly and slug flow, the momentum transfer between the phases is usually modelled by forces acting on the bubbles. These forces depend on the liquid flow field as well as on the size and the shape of the bubbles. To validate models for these forces a detailed database for vertical pipe flow is used. It contains not only the information on the radial distribution of bubbles of different size, but also information on the bubble size distribution. Measurements were done for a large number of combinations of gas and liquid superficial velocities and for two different pipe diameter (DN50 and DN200). An one-dimensional model, which resolves the variables in radial direction and which considers a large number of bubble size classes to account for the size effect, is used for an analysis of models for these forces. The results obtained by this model were compared to 3D results obtained by the commercial code CFX-5.7 for simplified cases with only one bubble class. The effect of the number of bubbles classes as well as the effect of the lateral extension of the bubbles were analysed. For the validation of the bubble forces measured bubble size distributions were taken as an input for the model. On basis of the assumption of an equilibrium of the lateral bubble forces, radial volume fraction profiles were calculated separately for each bubble class. In the result of the validation of different models for the bubble forces, a set of Tomiyama lift and wall force and the Favre averaged turbulent dispersion force was found to reflect the experimental data with best agreement. Some discrepancies remain at high liquid superficial velocities.
Keywords: Two-phase flow, bubble, bubble forces, modelling, CFD
  • Lecture (Conference)
    42nd European Two-Phase Flow Group Meeting, 23.-25.06.2004, Genua, Italy
  • Contribution to proceedings
    42nd European Two-Phase Flow Group Meeting, 23.-25.06.2004, Genua, Italy, paper E1

Publ.-Id: 6342 - Permalink