Regulation of Viscoelastic Instability by Crystallization of Particle Suspension

The viscoelasticity of a polymer solution can destabilize the shear flow and convert such flow into a steady primary flow plus an unsteady secondary flow, where the fully-developed secondary flow contains hierarchical flow structures. These flow structures typically have a power-law distribution in frequency. Here we report that adding particle suspension into a viscoelastic polymer solution regulates the secondary flow and disturbs the power-law distribution by introducing an unexpected rotational motion while suppressing other flow structures.

To understand this unusual behavior, we directly visualize the velocity field and particle structure formation in the flow geometry to reveal that such regulation originates from the crystallization of the particles into layered sheets under shear, even when the volume fraction of the particles is far lower than the requirement of the crystallization.

Finally, we show how to retrieve the power law distribution flow structures by inhibiting the crystallization with polydispersed particles. Our study highlights the interplay between the particle suspension and the viscoelastic fluid flow also the limitation of viewing the particle suspension as a single phase.