Backward-Facing Step Flow in Microchannels Using Microparticle Image Velocimetry
Abbreviated Journal Title
J. Thermophys. Heat Transf.
Thermodynamics; Engineering, Mechanical
Flow at a backward-facing step feature (1:5 expansion ratio) in a microchannel has been studied using microparticle image velocimetry. The onset and development of a recirculation flow was studied as a function of flow rate. The onset of recirculation was initiated at flow rates that correspond to Reynolds numbers, Re > 95. The dimensions are such that recirculation flow has a three-dimensional structure and is expected to vary with the depth coordinate. Because of volume illumination, most microparticle-image-velocimetry measurements provide two-dimensional averaged flow profiles. Flow at the backward-facing step offers the opportunity to investigate the ability of resolving the depth dependency by conventional microparticle image velocimetry in relevance to two parameters: variation of the focus plane depth z* and using variable time intervals for particle-image-velocimetry image pairs Delta t. The ensemble cross-correlation algorithm was found to be insensitive to the variation of z* for low magnification (4x) but was able to resolve the parabolic nature of flow across the depth of the channel, when high magnification objective lenses were used (20x). For a given flow rate and constant z*, the variation of At resulted in quantitatively and qualitatively different flow patterns, suggesting that Delta t is an indirect means Delta t of resolving the depth as the correlation algorithm locks onto a flow plane with particles moving at a speed that can be resolved with the given process parameters and time interval.
Journal of Thermophysics and Heat Transfer
Article; Proceedings Paper
"Backward-Facing Step Flow in Microchannels Using Microparticle Image Velocimetry" (2011). Faculty Bibliography 2010s. 2132.