Abstract
Viscoelastic flows through microscale porous arrays exhibit complex path selection and switching phenomena. However, understanding this process is limited by a lack of studies linking between a single object and large arrays. Here, we report experiments on viscoelastic flow past side-by-side microcylinders with variable intercylinder gap. With increasing flow rate, a sequence of two imperfect symmetry-breaking bifurcations forces selection of either one or two of the three possible flow paths around the cylinders. Tuning the gap length through the value where the first bifurcation becomes perfect reveals regions of bistability and tristability in a dimensionless flow rate-gap length phase diagram.
Highlights
Since the advent of microfluidics in the early 2000s [1,2], geometries with length scales l ∼ Oð100 μmÞ have become a vital tool in experimental fluid dynamics
Flow past a single circular cylinder in a channel is an archetypal problem in fluid dynamics, and a “benchmark” for studying viscoelastic flows
The stagnation point downstream of a cylinder is a location where streamline curvature combines with strong velocity gradients, conditions that render viscoelastic base flows prone to linear instability [28,29,30,31,32]
Summary
Since the advent of microfluidics in the early 2000s [1,2], geometries with length scales l ∼ Oð100 μmÞ have become a vital tool in experimental fluid dynamics. For small G 1⁄4 0.500, as Wi exceeds Wi1 [Fig. 2(b)], elasticity dominates and the system undergoes a first transition from the low-Wi symmetric state to a diverging “D” state where the fluid avoids the gap between the cylinders and flows symmetrically around their sides.
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