Cavitation Inception and Evolution in 'Cavitation on a Chip' Devices at Low Upstream Pressures

The concept of "hydrodynamic cavitation on a chip" offers facile generation of cavitating flows in micro domains, which can be easily scaled-up by arranging short microchannels (micro-orifices) in cascade formations. In this regard, micro-scale cavitation in an energy efficient test rig has the potential of increasing utilization possibilities of cavitation in a wide range of applications such as liquid phase exfoliation. In this study, a new experimental test rig was constructed to generate micro-scale hydrodynamic cavitation. This setup enables cavitation bubble generation at low upstream pressures through the control of the downstream pressure of the device. Particular attention was directed to the classification of flow patterns, scale effects and cavitating flow evolutions with in-depth categorization of underlying mechanisms such as Kelvin-Helmholtz instability. Cavitation inception appeared in the form of a single bubble. The appearance of different attached cavitating flow patterns within the microfluidic device were accompanied by new physics, which revealed that cavitation generation and development are affected by the existence of various fluid flow phenomena, particularly the jet flow. The outcome of this study makes 'hydrodynamic cavitation on a chip' attractive for applications, where the cavitation effects are sought in the presence of multiphase fluid flows.