Flow patterns in 4:1 micro-contraction flows of viscoelastic fluids

Springer Science and Business Media LLC - Tập 27 - Trang 65-73 - 2015
Daewoong Lee1, Kyung Hyun Ahn1
1School of Chemical and Biological Engineering, Institute of Chemical Process, Seoul National University, Seoul, Republic of Korea

Tóm tắt

In this paper, the flow pattern of viscoelastic fluids flowing inside a 4:1 planar contraction microchannel was investigated and quantitatively analyzed. A wide range of Weissenberg number flows of poly(ethylene oxide) solutions were observed while maintaining low Reynolds number (0.01 > Re). As the shear rate or fluid elasticity was increased, a transition from steady to unsteady flow was observed. In the steady flow region, the flow pattern was Newtonian-like, progressed to a divergent flow where the upstream flow pattern was distorted due to elasticity, and then a vortex developed at the upstream corners. The vortex, which was stable at first, fluctuated with a certain period as the Weissenberg number increased. The oscillating vortex was symmetric at first and became asymmetric with various patterns. As the elasticity increased further, the vortex randomly fluctuated without any time period. The Lyapunov exponent for the change in vortex size was positive, meaning that the flow was spatially chaotic. This paper systematically analyzed the flow patterns of the elastic fluids in the micro-contraction flow, which included; Newtonian-like flow, divergent flow, oscillating flow with symmetry, oscillating flow with asymmetry, and chaotic flow.

Tài liệu tham khảo

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