Implementation and Validation of Non-Drag Interfacial Forces in CFX-5.6

In Eulerian-Eulerian modeling of multiphase flow, closure models are needed for interfacial forces. The present work was concentrated on the non-drag forces, namely the lift, virtual mass, turbulent dispersion and wall lubrication force. They are reported to be mainly responsible for the gas volume fraction distribution in a vertical bubbly flow. Different models were proposed in the literature for each of these forces. In this work, we implemented a number of non-drag force models in the Eulerian multiphase flow package of the commercial code CFX-5.6 in order to enhance its application range. Extensive numerical experiments were carried out in order to examine their numerical properties (convergence characteristics, grid dependence of the results) and to
evaluate their validity. The evaluation was based on the experimental database for upward air-water flows in a vertical pipe established at Forschungszentrum Rossendorf (FZR) using the fast wiremesh sensor measurement technique. In all simulations a zero-equation model was used for the dispersed phase whereas two different turbulence models, namely the $k$-$\varepsilon$ and SST model, were investigated for the liquid phase. The bubble induced turbulence was taken into account by the Sato model. Fairly good agreements were observed between the numerical solutions and measurements for all test cases when the SST model was chosen together with the Tomiyama correlations for the lift and wall lubrication force and the {Favr\'e}-Averaged Drag (FAD) model for the turbulent dispersion force due to Burns (2001). The results clearly show the advantage of the FAD model over the widely applied model by Lopez de Bertodano et al.(1994). In addition, the investigation also indicates that further efforts in multiphase phase flow turbulence modeling and in near-wall treatment are very necessary.