Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

1 Publication

Two phase flow 1D turbulence model for poly disperse upward flow in a vertical pipe

Al Issa, S.; Lucas, D.


A 1D test solver was developed in recent years for the modeling of two phase bubbly flow in pipe geometry. The solver considers number of bubble classes and calculates bubble-size resolved void fraction profiles in radial direction. A successful implementation was achieved regarding bubble forces models (non-drag forces). Discrepancies appeared when coalescence and breakup rates are significant. These rates depend upon local turbulent values, which are possible reason for shortcomings in calculating coalescence and breakup rates. Originally the test solver is equipped by Sato model (Sato et al. 1981) which accounts for turbulence via shear- and bubble-induced viscosities calculated out of empirical correlations. One-equation for the turbulent kinetic energy was considered. In order to improve the local values of turbulence parameters the existing turbulence model was replaced by two-equation turbulence model. The new model accounts for the bubble-induced turbulence via source term taken from literature. Comparisons between new and old turbulence modeling against experimental data showed better agreement of the new model. The experiments covered wide range of water and air superficial velocities for upward bubbly flow in two pipe’s diameters: 50 mm and 200 mm. Main feature of new calculations is providing values of turbulence parameters for application in coalescence and breakup models. A comparison with CFX 5.7 calculations in 50 mm pipe showed better calculation results when applying the source term. An implementation of the source term into CFX calculations is planned.

Keywords: Poly-disperse; bubbly Flow; bubble-induced turbulence; CFD

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