Interfacial dynamics: drops & particles

Department of Mechanical Engineering, Texas A&M University

This talk consists of two parts that consider the dynamics of the fluid-fluid interface for two different systems: droplets and particle-laden flows. In the first part of the talk, the stability of a partially wetting drop against wind is experimentally tested inside a wind tunnel and is rationalized by a simple, quasi-static model of a `depinning? droplet. The reduced model incorporates the phenomenological description of the boundary layer into droplet dynamics and successfully captures the observed critical droplet behavior.? In the second part of the talk, we report a particle-induced fingering instability when a mixture of particles and viscous oil is injected radially into a Hele-Shaw cell. The experimental results show that the onset and characteristics of fingering are most directly affected by the particle volume fraction but also depend on the ratio of the particle to gap size. The physical mechanism behind the instability and a quantitative model based on the suspension balance approach are also discussed.