Numerical simulation of single bubble motion fragmentation mechanism in Venturi-type bubble generator

Abstract

Microbubbles have been widely used in power, chemical, mining and petroleum applications to improve energy efficiency. The venture-type bubble generator can improve reaction efficiency in chemical engineering as an efficient bubble generation method. Studying the flow field and bubble bursting mechanism can enhance the bubble generation performance. The volume of fluid (VOF) multiphase flow model was used in the Open Field Operation and Manipulation (OpenFOAM) framework to study the deformation and fragmentation behaviour of a single bubble in a Quasi three-dimensional. The relationship between the mechanism of bubble breakup and the flow field in the diverging section of a Venturi-type bubble generator was revealed. The reasons for the uneven distribution of bubble size were analyzed and discussed. The numerical simulation result shows that the fragmentation of a single bubble injected by the converging section is more substantial than that injected by the throat in the axial direction. Bubble fragmentation occurs mainly in the diverging section. The bubble's trajectory is highly similar to the vortex trajectory of the diverging section. The size of sub-bubbles generated by single bubble fragmentation decreases with the diverging angle and liquid flow rate increase. The differential distribution of turbulent kinetic energy in the radial position directly leads to the uneven distribution of the bubble size of the broken bubbles. As the liquid Reynolds number increases, static and dynamic erosion breakup are more prominent. The size of the sub-bubbles is much smaller.