Pattern formation in suspensions

In this talk, we examine the spontaneous emergence of particle clusters inside the suspension that is radially displacing air inside a Hele-Shaw cell. This pattern formation is driven by the interfacial instability that follows the particle accumulation at the suspension-air interface. We observe that the key characteristics of the pattern and its growth (i.e. shape and wavenumber) are directly affected by the nature of particle accumulation leading up to the instability. In particular, we focus on the regime in which particles form a discrete band of packing on the interface; the subsequent break-up of the particle band causes the formation of the particle islands inside the suspension that evolve over time. We also discuss the balance of the stabilizing and destabilizing effects inside the particle band which rationalize the observed wavelength.