Scaling of Microbubble Generation in a T-junction

Microbubble generation in a microfluidic T-junction was investigated in the context of artificial nuclei seeding of hydrodynamic facilities. Microbubble size distribution and production rate were investigated for a range of air, water and outlet pressures using high-speed shadowgraphy. The generator was found to produce a train of monodisperse bubbles approximately 100um in diameter across a range of operating conditions. The only exception to this being the cases with a large difference between the air and water supply pressures where bubble coalescence was prominent. An empirical scaling law depicting the dependence of bubble diameter on the operational conditions was developed by fitting all the data using least-squares regression. Bubble production frequency was found to exhibit a quadratic increase with an increase in the difference between the air supply and the outlet pressure. Production frequencies in the range 0 kHz to 3.5 kHz were observed across the range of investigated conditions. The reported work demonstrates the T-junction to be a robust device for monodisperse microbubble generation and a useful tool for experimental modelling of nucleation effects in hydrodynamic facilities.