The Hydrodynamic Cavitation Manifestation in Small Chips

Cavitation is a phase change phenomenon generated by the static pressure reduction of a liquid medium at a constant temperature. This process has been considered as a disadvantageous mechanism in most turbomachinery systems, however, its potential in releasing energy at the bubble collapse stage has received lots of attention in recent decades. Particularly, the applicability of this phenomenon in micro scale gives rise to the research studies in different fields, i.e., wastewater treatment and medical imaging. In this study, microfluidic devices housing small microchannels have been fabricated to study the generation of the cavitating flow patterns bubbles. The main focuses in this work are on the surface and side wall roughness together with the size reduction effects on cavitation bubble generation. Accordingly, the microfluidic devices were fabricated using the techniques adopted from semiconductor based micro- fabrication. The experiments were performed at relatively higher upstream pressure, 4 to 7 MPa, to investigate the durability of the devices and flow patterns features. The results show that the side wall roughness elements are very effective in the small microchannels in terms of facile cavitating flow generation, while the size reduction in the diameter of the channel does not lead to intensified cavitating flow necessarily. The results show that the cavitation bubbles extended to the outlet of the side wall roughened microchannel even at the upstream pressure of 5.5 MPa, while the supercavitation flow regime was observed at high upstream pressure of 7 MPa.