(257f) Complex Fluids in Confined Flows: Squishing, Intermittency, and Jamming

Intermittency and clogging of complex fluids flowing through small spaces can occur nearly anywhere: in the porous media of the earth, in industrial flows through hoppers, in water filters, 3D printing nozzles, and in some of the worst instances, in our blood vessels. These examples include flows of colloidal particles, granular material, crosslinking polymers, and multicomponent systems. Despite the differences in the type of complex fluid involved, some aspects of clogging are universal, like its stochastic nature and the importance of the constituent material properties. Our research explores intermittency, clogging, and flow in micro- and macroscopic flows. In colloidal and granular flows, we vary the softness of the constituent particles and the fraction of soft particles in a mixture. In this way we elucidate how softness controls phenomena like clogging and avalanches. Polymers crosslinking in situ in flow through microchannels also exhibit intermittent dynamics reminiscent of avalanches. In these flows, gelation, deposition, and ablation can occur repeatedly and persistently. Intriguingly, despite the low-Re nature of the flow, we find signatures of chaotic behavior as conditions approach regions of complete failure. This model system might represent situations encountered in polymer flows in 3D printing applications, or, in a greatly simplified way, two of the final steps in the coagulation cascade.