Numerical and experimental investigation of the effect of channel geometry on cavity formation in microfluidic channels

Abstract

Cavitation formation in low pressure regions of a flow is a chaotic distortion in fluid mechanics. Due to the complicated nature of multiphase flows, its modelling is expensive in terms of time and computational power. Opensource softwares such as OpenFOAM reduce license expenses and provide a developer friendly environment to simulate these types of complicated flows. In this thesis, by using OpenFoam software, several different geometries that cause cavitation are investigated. Presented results are compared with both literature and supported by experimental results. Experiments are carried out in microfluidic chips that are fabricated with soft lithography technique; fluorescent particles were introduced in the flow and cavity formation was observed under a fluorescent camera. Results showed that, OpenFOAM is well capable of predicting the cavitation formation in small scales. It was observed that increasing channel width reduces the pressure difference causing bubbles to form in higher input pressures. It was also seen that decreasing the channel width causes friction and viscous forces to dominate and reduce the velocity of fluid preventing the cavitation to form. Overall the modelling of cavity formation in microchannels with varying width and cross sectional profile were successfully accomplished and results were verified with experiments.