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Intermittent flow in yield-stress fluids slows down chaotic mixing
D M Wendell1, F Pigeonneau, E Gouillart
1Surface du Verre et Interfaces, UMR 125 CNRS/Saint-Gobain, 39, quai Lucien Lefranc, F-93303 Aubervilliers Cedex, France.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 17, 2013
Summary
Yield-stress fluids mix slower than Newtonian fluids due to intermittent flow and peripheral region effects. Chaotic advection is reduced, especially when stirring elements synchronize, slowing particle stretching.
Area of Science:
- Fluid dynamics
- Rheology
- Non-Newtonian fluid mechanics
Background:
- Chaotic advection is a key mechanism for fluid mixing.
- Yield-stress fluids exhibit complex flow behaviors not seen in Newtonian fluids.
- Understanding mixing in complex fluids is crucial for industrial processes.
Purpose of the Study:
- To experimentally investigate and compare the chaotic mixing of Newtonian and yield-stress fluids.
- To elucidate the mechanisms behind reduced mixing in yield-stress fluids.
- To validate findings through numerical simulations.
Main Methods:
- Utilizing a rod-stirring protocol within a rotating vessel.
- Conducting experimental studies on both Newtonian and yield-stress fluids.
- Performing numerical simulations to confirm experimental observations.
Main Results:
- Yield-stress fluids demonstrate significantly reduced mixing compared to Newtonian fluids.
- Intermittent fluid flow and the influence of the peripheral region were identified as key factors.
- Synchronization of stirring elements led to anomalously slow mixing and repeated particle stretching.
Conclusions:
- Yield stress fundamentally alters chaotic advection, hindering efficient mixing.
- The interplay between intermittent flow and fluid boundaries dictates mixing efficiency.
- Numerical simulations corroborate the experimental findings on reduced mixing in yield-stress fluids.
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