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首页> 外文期刊>Physics of fluids >Flow visualization of cavitating flows through a rectangular slot micro-orifice ingrained in a microchannel
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Flow visualization of cavitating flows through a rectangular slot micro-orifice ingrained in a microchannel

机译：空化流过在微通道中根深蒂固的矩形槽微孔的流动可视化

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Multifarious hydrodynamic cavitating flow patterns have been detected in the flow of de-ionized water through a 40.5 mu m wide and 100.8 mu m deep rectangular slot micro-orifice established inside a 202.6 mu m wide and 20 000 mu m long microchannel. This article presents and discusses the flow patterns observed at various stages of cavitation in the aforementioned micrometer-sized silicon device. Cavitation inception occurs with the appearance of inchoate bubbles that emerge from two thin vapor cavities that emanate from the boundaries of the constriction element. A reduction in the cavitation number beyond inception results in the development of twin coherent unsteady large vapor cavities, which appear just downstream of the micro-orifice and engulf the liquid jet. The shedding of both spherical and nonspherical vapor bubbles and their subsequent collapse into vapor plumes downstream of the orifice occurs intermittently. A further reduction in the exit pressure only aids in the elongation of the two coherent cavities and produces two stable vapor pockets. Additionally, interference fringes are clearly observed, showing that the vapor pocket has a curved interface with liquid. At low cavitation numbers, the flow undergoes a flip downstream and the two vapor pockets coalesce and form a single vapor pocket that is encircled by the liquid and extends until the exit of the microchannel. The cavitating flow patterns are unique and are markedly different from those reported for their macroworld counterparts. Evidence of pitting due to cavitation has been observed on the silicon just downstream of the micro-orifice. It is therefore apparent that cavitation will continue to influence/impact the design of high-speed MEMS hydraulic machines, and the pernicious effects of cavitation in terms of erosion, choking, and a reduction in performance will persist in microfluidic systems if apposite hydrodynamic conditions develop. (c) 2005 American Institute of Physics.
机译：在去离子水流中发现了多种流体动力空化流型，这些去离子水流通过在202.6μm宽和20000μm长的微通道内建立的宽40.5μm和深100.8μm的矩形缝隙微孔。本文介绍并讨论了在上述微米级硅器件中在空化的各个阶段观察到的流动模式。空化开始发生时出现早期气泡，气泡出现在两个狭窄的蒸汽腔中，这些蒸汽腔从收缩元件的边界散发出来。空化次数的减少超过开始时会导致形成双相干非稳态大蒸气腔，该蒸气腔恰好出现在微孔的下游并吞没了液体射流。球形和非球形蒸气气泡的脱落以及它们随后破裂成小孔下游的蒸气羽流间歇地发生。出口压力的进一步降低仅有助于两个相干腔的伸长，并产生两个稳定的蒸汽囊。此外，清楚地观察到干涉条纹，表明蒸气囊与液体具有弯曲的界面。在低空化数下，流向下游翻转，两个蒸汽囊合并并形成单个蒸汽囊，该蒸汽囊被液体环绕并一直延伸到微通道出口。空化流态是独特的，并且与宏观世界中所报道的那些明显不同。已经在微孔下游的硅上观察到由于气蚀引起的点蚀的迹象。因此，很明显，空化将继续影响/影响高速MEMS液压机的设计，如果出现合适的流体力学条件，则在微流体系统中，空化在腐蚀，阻塞和性能降低方面的有害影响将持续存在。 。 （c）2005年美国物理研究所。

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