Numerical investigation of a single intermediate-sized bubble in horizontal turbulent channel flow

Abstract

Air lubrication systems have gained considerable popularity as a promising drag reduction technology in recent years. However, numerical simulations of intermediate-sized bubbles are quite challenging because of the numerical diffusion of the conventional method and the high deformability of the bubbles. This hinders the study of the physical mechanisms involved in a variety of phenomena in such types of bubbles, such as the bubble–liquid interaction effect, high bubble deformation, and flow in the liquid film generated above the bubble. In this study, a solver, viz. interIsoFoam of OpenFOAM, which is directly captured by the improved volume of fluid method, was applied to solve the gas–liquid interface problem. We established the numerical procedure by dividing it into three stages and validating the accuracy of the given solver to minimize numerical errors such as smearing the volume fractions. The numerical results for variables such as the bubble shape, the skin friction of the liquid film, and the instantaneous momentum flux display trends similar to those observed in the experiments. The calculated bubble shows a high skin friction in the secondary flow, which corresponds to the distribution of streamwise vortices in the secondary flow.

Keywords

• two-phase flow
• turbulence
• drag reduction
• bubble deformation