Droplet spreading on immiscible liquid layers

The technical challenges associated with droplets depositing and spreading on oily-soft surfaces is of significant interest to many industries including printing, paint and agriculture. However, our understanding of the fluid dynamics encountered in these complex systems is severely lacking due to a limited number of fundamental studies.  The immiscible interaction of viscoelastic and Newtonian liquids has recently highlighted some interesting flow phenomena referred to as the inverted Cheerios effect, where droplet migration is dependent on both the fluid-fluid interfacial tension and the fluid(s) viscoelasticity. To advance our understanding of the fluid dynamics in these complex dual fluid systems, and to get a handle on the governing parameters, a range of experimental and computational techniques will be employed. High resolution, high-speed imaging combined with PIV will be used to study the incipient migration and spreading of droplets on thick-liquid films. The generated data will be used to support theoretical model development which will be implemented in a Leeds simulation code (based on the lattice Boltzmann method) that has recently been used successfully for modelling Newtonian droplet impact and coalescence dynamics on complex but rigid (rough and chemically non-uniform) surfaces. The project will shed light on the complex flows encountered when a viscoelastic droplet spreads on an underlying liquid film.