Numerical research on bubble formation process in microchannel using diffuse Interface method

Abstract

Gas-liquid two-phase flow is an important research project in microfluidics. The mechanism of bubble formation still needs more study to control the bubble’s size precisely. As the radius of bubble is about 0.1 mm to 0.6 mm in the simulation, the energy used to overcome the surface tension can’t be neglected. By using the Cahn-Hilliard equation, the diffuse interface method can not only track the fluid interface, but also have a reasonable reduction of the total energy of the system. So the formation of bubble in microchannel is simulated based on the diffuse interface method in this paper. At first, we compare the numerical results with the experiments and find that they agree well with experiments. It indicates that this method can be used to simulate the bubble formation process in the microchannel. Then, the influence of flow rate, gas-liquid flow ratio, surface tension, viscosity, the entrance length and width of the main channel are discussed. The results show that the pressure difference is the main reason for the bubble formation and the change of liquid-gas flow ratio and liquid flow rate have great effects on the formation process. In addition, smaller surface tension can cause the inlet liquid pressure decrease and reduce expansion time to accelerate the formation process. And greater shear force leads to a long bubble neck when the tip of gas phase don’t fill the main channel. Eventually, our work also reveal that bubbles get bigger in a logarithmic tendency with the entrance of main channel widening.