Stability considerations associated with the meniscoid particle band at advancing interfaces in Hele-Shaw suspension flows

In the free surface flow of dense suspensions in confined domains, Spontane ous particle enrichment occurs in the region adjacent to the free surface w ith an attendant increase in the effective viscosity. We present experiment al evidence that this particle accretion introduces stability consideration s that would otherwise not exist if the suspension remained uniform. For co nditions favoring global stability, a local fingering instability can occur in the accretion band. For conditions favoring global instability, accreti on can suppress the global growth of viscous fingers at the interface.