Bubble formation from an orifice in liquid cross-flow

Abstract

The formation of gas bubbles by submerged orifices in a cross-flowing liquid is encountered in many industrial applications. It is therefore important to understand the dynamics of bubble formation and to accurately predict the bubble detachment characteristics under such situations. In the present work, the process is numerically studied using the Local Front Reconstruction Method (LFRM), a Front Tracking Direct Numerical Simulation method that enables the simulation of interface merging and breakup. Experiments of bubble formation subjected to cross-flow induced shear are also performed to provide data for the validation of the numerical simulations. The predictions of the bubble shape and the detached bubble volume obtained by the numerical model show good agreement with the experimental results. The validated numerical model is then used to study the effects of volumetric gas flow rate and fluid physical properties on the bubble detachment characteristics under various shear rates in the quasi-static bubble growth regime. The simulation results show that the shear flow advances the bubble detachment and decreases the bubble size. Consequently, the bubble formation frequency and the detached bubble size can be controlled by exerting different shear rates. At higher shear rates, the simulated bubbles are highly deformed due to the drag force created by the tangential liquid flow and the influence of liquid properties on the bubble detachment characteristics becomes less significant.