Title: Clogging and intermittency in microfluidic and hopper flows

Author (Invited): Sara Hashmi, Northeastern University

Abstract:

Clogging is ubiquitous, from the colloidal scale to the granular scale, in situations when particle sizes approach the size of constrictions in the flow path. In this talk we explore two very different clogging situations in which avalanche-like dynamics appear. On the microfluidic length scale, suspensions of rigid colloids clog long, gently tapered pores in a discontinuous fashion. Clogs form stochastically, and the formation of any new clog along the length of the pore prevents particles from reaching clogs already present downstream. The clogs are very stable against flow perturbations. Despite this, statistical analysis of clog length reveals features reminiscent of those seen in avalanches. On the macro-scale, we explore hopper flows of granular mixtures of soft and rigid particles. We find that, surprisingly, despite differences in friction between the particle types, both softness and geometry play prominent roles in determining clogging probability and avalanche dynamics.