Investigation of drag models for simulation of gas-liquid two-phase flow systems

The accurate prediction of gas-liquid two-phase flows in industrial systems relies on the careful selection of interfacial force models, particularly the drag force, which dominates momentum transport between phases. This study numerically investigates six widely adopted drag coefficient models using the Eulerian-Eulerian two-fluid framework coupled with the homogeneous "MUltiple Size" Group (MUSIG) population balance model in ANSYS CFX 14.5. The primary objective is to evaluate the predictive performance of these models in capturing local radial gas volume fractions under polydispersed bubbly flow conditions. Simulations were validated against benchmark experimental data from Lucas et al. and Monrós-Andreu et al., which cover a range of superficial gas and liquid velocities. Mean absolute error (MAPE) was used as the main error indicator for model evaluations. The results from the study show that while all models qualitatively behaved differently depending on the test case considered, the model by Grace et al. offered superior predictions (MAPE < 6% for all test cases) within the core region for the MTLoop dataset obtained from Lucas et al. Additionally, all models performed relatively poorly near the wall when compared with the Lucas et al. dataset. In contrast, all models performed better when compared with the Monrós-Andreu et al. dataset, which does not involve transition regimes or very high gas superficial velocities. Notably, the Simonnet et al. model exhibited enhanced performance in high gas superficial velocity cases due to its incorporation of swarm effects. Across both datasets, all models showed better agreement to some extent with experimental data in the pipe core region than near the wall. The insights from this work are valuable for selecting appropriate interfacial force models for industrial simulations and highlight the need for developing drag models for the dynamics of bubbly flows.