Picture map of Europe with pins indicating European capital cities

Open Access research with a European policy impact...

The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of Open Access research papers by Strathclyde researchers, including by researchers from the European Policies Research Centre (EPRC).

EPRC is a leading institute in Europe for comparative research on public policy, with a particular focus on regional development policies. Spanning 30 European countries, EPRC research programmes have a strong emphasis on applied research and knowledge exchange, including the provision of policy advice to EU institutions and national and sub-national government authorities throughout Europe.

Explore research outputs by the European Policies Research Centre...

Jamming and unjamming of concentrated colloidal dispersions in channel flow

Campbell, A.I. and Haw, M.D. (2010) Jamming and unjamming of concentrated colloidal dispersions in channel flow. Soft Matter, 6 (19). pp. 4688-4693. ISSN 1744-683X

[img]
Preview
PDF
c0sm00110d.pdf - Final Published Version

Download (289kB) | Preview

Abstract

We investigated the pressure driven flow of concentrated colloidal dispersions in a converging channel geometry. Optical microscopy and image analysis were used to track tracer particles mixed into dispersions of sterically stabilized poly(methyl methacrylate) (PMMA) spheres. The dispersions were drawn into a round \unit[0.5]{mm} capillary at one of two pump speeds ($\equiv$ applied pressure): $v_1=\unit[0.245]{ml\,\, min^{-1}}$ and $v_2=\unit[0.612]{ml\,\, min^{-1}}$. We observed that the dispersions at particle volume fractions $\phi\leqslant0.50$ followed Hagen-Poiseuille flow for a simple fluid; i.e. the mean flow rate $\langle V\rangle$ is approximately proportional to pressure drop (pump speed) and inversely proportional viscosity $\eta$. Above this concentration ($\phi\geqslant0.505$), the dispersions exhibit granular-like jamming behavior with $\langle V\rangle$ becoming independent of the pressure drop. However, at the highest applied pressure ($v_2$), the dispersions are able to unjam and switch from granular-like behaviour back to a simple hard-sphere liquid like system, due to the formation of rotating vortices in the spatial flow pattern. This mechanism is consistent with computer simulations of granular systems and supports for example proposed explanations of anomalously low friction in earthquake faults.