Interface tracking simulation of bubbles in clean and contaminated systems

다국어 초록 (Multilingual Abstract)

An interface tracking method based on a level set method for simulating bubbles in clean and contaminated systems is presented. Effects of the numerical treatment of the viscous and surface tension forces on predicted interface motion are investigated. A ghost fluid method is the best for both systems. The harmonic mean of the viscosity for the smeared-out interface method gives good evaluations of viscous stress at the interface. However this method causes large errors if the Marangoni force acts on the interface. The arithmetic mean gives some errors, which can be reduced by increasing the spatial resolution. Numerical simulations of nearly spherical bubbles and a deforming bubble are also carried out. These simulations show that the interface tracking method gives accurate predictions of bubble motion and is of great use in investigation of effects of surfactant on bubble motion. Effects of surfactant on the terminal velocity of a Taylor bubble in low Morton number systems are therefore investigated using the interface tracking method. The numerical results confirm that the reduction of surface tension near the bubble nose is the cause of the increase in terminal velocity of a Taylor bubble at low Eotvos numbers.