Viscosity effect on regular bubble entrapment during drop impact into a deep pool

Viscosity plays an important role in regular bubble entrapment during drop impact into a deep pool. In this paper, the volume of fluid (VOF) model in conjunction with the continuum surface force (CSF) model is used to investigate the dynamics of regular bubble entrapment in fluids with a range of viscosities (η=0.1-10.0×10^-3Pas). Time evolutions of the crater profiles and crater depths in different viscous fluids are compared. Numerical results show that the damping effect of the viscosity on capillary wave propagation leads to an increase in the lower limit of the regular bubble entrapment region, whereas the damping effect on crater cusp reversal dynamics leads to an increase in the upper limit. Based on the timing estimate, a scaling model for the effect of viscosity on the limits of the regular bubble entrapment region is provided. Finally, the distribution of bubble size as a function of the capillary number is investigated.