- 1:30 PM
90e

Interfacial Flows In the Presence of Additives

Omar K. Matar, Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom and Richard V. Craster, Mathematics, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom.

The presence of additives, which may or may not be surface active,

can have a dramatic influence on interfacial flows. The presence of

surfactants alters the interfacial tension and drives Marangoni flow

that leads to fingering instabilities in drops spreading on

ultra-thin films. Surfactants also play a major role in coating

flows, foam drainage and may be responsible for the so-called

``super-spreading" of drops on hydrophobic substrates. The addition

of surface-inactive nano-particles to thin films and drops also

influences the interfacial dynamics and has recently been shown to

accelerate spreading and to modify the boiling characteristics of

nanofluids. These findings have been attributed to the structural

component of the disjoining pressure resulting from the ordered

layering of nanoparticles in the region near the contact line. In

this talk, we present a collection of results which demonstrate that

the above-mentioned effects of surfactants and nano-particles can be

captured using long-wave models.