Multifarious hydrodynamic cavitating flow patterns have been detected in the flow of de-ionized water through a wide and deep rectangular slot micro-orifice established inside a wide and 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.
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November 2005
Research Article|
November 17 2005
Flow visualization of cavitating flows through a rectangular slot micro-orifice ingrained in a microchannel
Chandan Mishra;
Chandan Mishra
Department of Mechanical, Aerospace and Nuclear Engineering,
Rensselaer Polytechnic Institute
, Troy, New York 12180
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Yoav Peles
Yoav Peles
a)
Department of Mechanical, Aerospace and Nuclear Engineering,
Rensselaer Polytechnic Institute
, Troy, New York 12180
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a)
Author to whom correspondence should be addressed. Telephone: 518-276-2886; fax: 518-276-2623; electronic mail: pelesy@rpi.edu
Physics of Fluids 17, 113602 (2005)
Article history
Received:
February 08 2005
Accepted:
September 26 2005
Citation
Chandan Mishra, Yoav Peles; Flow visualization of cavitating flows through a rectangular slot micro-orifice ingrained in a microchannel. Physics of Fluids 1 November 2005; 17 (11): 113602. https://doi.org/10.1063/1.2132289
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