Modeling of interfacial momentum exchange for wall-bounded bubbly flows

The two-fluid model based on Eulerian-Eulerian approach has been widely used for simulating two-phase flows in industrial applications due to much less CPU requirement as compared to interface tracking methods. However, the two-fluid approach needs accurate modeling for interfacial mass, momentum, and heat transfers between phases. The important interfacial momentum exchange terms include drag, shear-induced lift, and wall-induced lift forces. In particular, it is important to accurately model the wall effect in order to predict 'wall peaking' or 'core peaking' phenomena observed in bubbly pipe flow. However, the wall effect is not fully understood yet and wall force coefficient in previous studies has a wide range of values, probably tuned to the experimental results. Therefore, to improve the performance of the two- fluid model for the bubbly flows, we are to propose a new model considering the wall effect on drag and lift forces. To do so, we separately perform resolved simulations for the flow around a moving sphere located near the wall. To evaluate the accuracy of the present model, numerical simulations based on two-fluid models are conducted for laminar bubbly flows available in the literature. The radial distributions of void fraction, liquid velocity, and bubble velocity show a reasonably good agreement with those from available numerical and experimental results.