Study On The Direct Numerical Simulation Of Gas-liquid Interface Based On The Front Tracking Method

The tracking of phase interface in multiphase flow simulation process is difficult. For the purpose of high accurate gas- liquid interface, the Front Tracking Method(FTM) based on density tracking was used to simulate gas- liquid interface flow,and the surface tension was added. By using the Finite Volume Method(FVM), the varied viscosity was simulated. By comparing with the experimental results, the interface morphology of a single droplet falling has been validated. Based on the front tracking method,a density interface tracking system was built to track bubble interface. Moreover, the situation before and after front track ing were analyzed. The results show that: the front tracking method is able to simulate the migration situation of gasliquid interface, and it shows much clearer interface of density which represents a good agreement with the actual physical laws.By adding the surface tension and using the finite volume method to dispose viscosity, the interface shape simulation of the single bubble rising in viscous fluid was competed. The calculation model was verified by comparing with the experimental results which show the same shape change rules in the same order of magnitude of Eo N umber and Mo Number. The coaxial two bubbles rising process were computed to compare with other numerical simulation method. The result shows that the bubbles’ interface morphology shares the same change. However, FTM simulation displays much clearer interface. Further study on the coaxial two bubbles rising for the dynamic characteristics including pressure distribution and speed of change were accomplished. The results show that the two bubbles have there own pressure center area which change the bubble motion speed greatly and lead to interface morphology changing by spherical- bullet- oval shape. The two bubbles’ interaction force is weakening over time, and the two bubbles gradually merge into one bubble.The interaction of a buoyancy bubble with an elastic boundary and its oscillation process are complicated. Fully considering the effect of surface tension, viscosity and gravity, with the model of the bubbles rising freely to hit the free surface as the researched object and the free surface on the boundary deformation and speed as the main analyzed object, the mutual coupling of the bubble are analyzed by Front Tracking Method. The law of the bubbles’ velocity and the deformation in the rising process within and without the free surface were compared. The influence of different Eo Number for the various stages of the bubble velocity was analyzed in each high and low viscosity control region. Moreover, the Eo Number and Weber N umber were analyzed in the bubble rising of a free zone and the process of deformation in low viscosity control zone.