Micro-particle image velocimetry study on hydrodynamic characteristics of in-line and staggered micro pin fin arrays

Abstract

Detailed hydrodynamics in microchannels with in-line and staggered circular micro pin fin structures over Reynolds number ranging from 50 to 700 are experimentally studied with micro-particle image velocimetry. The velocity field, vortex structure and vorticity distribution is obtained and analyzed, and differences in flow behavior in the two arrangements are examined. The result indicates a delay in the onset of vortex shedding in micro pin fin arrays as compared to their macro scale counterpart due to the confinement effect of channel walls. Flow pattern in the in-line arrangement is featured by the microchannel-like main stream between the pin rows and the double vortex wake flow behind the pins, while flow in the staggered arrangement is characterized by the wavy main stream and a pair of accelerated flow streams on two sides of the pins. Vorticity bands along the sides of the wake region intensify with the Reynolds number, diffuse further downstream, but narrow in width. Visualization and data extraction results reveal that flow behavior in the staggered arrangement differs from that in the in-line arrangement in terms of a smaller area occupied by the low-velocity wake region and a more sufficient mixing of fluid.