Validation of Eulerian Multiphase Flow Models for Nuclear Safety Applications

The CFD package CFX-5 has been used to predict the development of upward directed gas-liquid flows in a vertical pipe. Under the assumption of monodisperse bubbles the dilute gas-liquid flow has been predicted using the Eulerian framework of multiphase flow modeling. The capabilities of the CFX-5 flow solver have been extended by taking into account additional non-drag forces like lift, turbulent dispersion and wall lubrication forces. Range of applicability and accuracy of the numerical model have been validated against measured gas void fraction profiles obtained at the MT-Loop test facility of the Forschungszentrum Rossendorf (FZR) in the bubbly flow regime. Best agreement of numerical results with experimental data could be obtained for a wide range of experimental conditions, if Menter s k-w Shear Stress Transport (SST) turbulence model has been used in combination with the Favre averaged drag (FAD) turbulent dispersion force model as derived by Burns [1]. Furthermore results of extensive numerical experiments [2] for the examination and comparison of different model formulations for the wall lubrication and turbulent dispersion forces are presented in this paper.