HYDRODYNAMIC CAVITATION IN FLOW THROUGH MICRO-CONSTRICTION ELEMENTS ENTRENCHED IN RECTANGULAR MICROCHANNELS

摘要

Hydrodynamic cavitation, the explosive growth and catastrophic collapse of vapor bubbles, has immense impact on the design and performance of hydraulic machinery in the macro world. However, cavitation in high-speed microfluidic systems has received scarce attention and hardly been reported. This article reports the presence of hydrodynamic cavitation in the flow of de-ionized water through 11.5-40micron wide rectangular slot micro-orifices entrenched inside 100-200micron wide microchannels. Pioneering experimental investigations on hydrodynamic cavitation in rudimentary microfluidic configurations such as slot micro-orifices has been presented and unique cavitating flow patterns have been identified. Assorted cavitating (two-phase) flow patterns including incipient, choking and supercavitation have been detected. Designers of high-velocity microfluidic systems, especially Power-MEMS devices, need to be aware of the deleterious effects of cavitation as it can significantly affect device performance. The effects of micro-orifice and microchannel size on cavitation have been discussed and results indicate the existence of strong scale effects. Incipient and choking cavitation numbers are observed to increase with increasing micro-orifice size, while the orifice discharge coefficient plummets once cavitation activity erupts. In addition, inlet pressure effects on several cavitation parameters have been discussed and compared with established macro-scale results. The cavitating flow patterns encountered are significantly influenced by the micro-orifice and microchannel size. Flow rate choking occurs irrespective of the inlet pressures and is a direct consequence of cavitation inside the micro-orifice. Cavitation hysteresis is observed but its effects are more marked for the smallest micro-orifice.