Disorder Suppresses Chaos in Viscoelastic Flows

Area of Science:

• Fluid dynamics
• Rheology
• Microfluidics

Background:

• Viscoelastic flows in microstructured geometries exhibit complex dynamics, transitioning to chaotic behavior at critical conditions.
• The impact of geometric disorder on the stability of these flows remains largely unexplored.

Purpose of the Study:

• To investigate how geometric disorder in microfluidic pillar arrays affects the onset of instabilities in viscoelastic flows.
• To elucidate the mechanisms by which disorder influences flow stability and chaotic transitions.

Main Methods:

• Experimental measurement of spatiotemporal velocity fluctuations in viscoelastic flow through microfluidic pillar arrays.
• Controlled variation of geometric disorder within the pillar arrays.

Main Results:

• A small degree of geometric disorder (∼10%) delays the onset of flow instabilities to higher speeds.
• Larger disorders (≥25%) suppress the transition to chaotic dynamics.
• Disorder creates preferential flow paths, favoring shear over extensional deformation and reducing polymer stretching.

Conclusions:

• Geometric disorder can stabilize viscoelastic flows in microfluidic devices.
• The findings offer insights into controlling complex fluid behavior in microstructured systems through geometric modifications.