The dependence of wall lubrication force on liquid velocity in turbulent bubbly two-phase flows

Abstract

Based on the significance of a computational fluid dynamics (CFD) simulation of dispersed two-phase flow systems in many engineering fields, especially in nuclear energy systems, extensive analytical and numerical studies of wall lubrication force for vertical upward turbulent bubbly two-phase flow are presented. An analytical expression of the wall lubrication force considering the effect of liquid velocity is developed and analyzed. A numerical methodology for evaluating the wall lubrication force coefficients is proposed, which is based on the assumption that the balance of the forces acting on a bubble perpendicularly to the flow direction determines the establishment of radial void fraction profiles. Wall lubrication force coefficients are determined based on a reasonable agreement in radial void fraction profiles between numerical results predicted by the CFD EAGLE (elaborated analysis of gas–liquid flows evolution) code and extensive experimental database in the open literature as well as experiments performed at the Korea Atomic Energy Research Institute-vertical air–water loop test facility. Liquid velocity dependence of wall lubrication force is clearly shown in both analytical and numerical ways in the present study, and new correlations are then proposed for the wall lubrication force coefficients.