Projects per year
Abstract
When droplets of high concentration wet powder impact on a solid surface, the large stresses that build up upon impact may convert them to a stable system of dry granules. Dilation/jamming has been proposed to explain such powder granulation processes. Stress causes dilation of particles through the droplet surface, against capillary pressure, roughening the surface on the scale of the constituent particles. Under the right conditions of stress magnitude and particle concentration, the droplet jams internally in response to capillary pressure, forming a mechanically stable granule. This remains a tentative model of granulation, which despite its importance in process industries ranging from minerals to foods to detergents, is still imperfectly understood. This work presents the preliminary results of drop impact experiments of a suspension of near hard-core colloidal particles, with the purpose to investigate the impact morphology in the presence of shear thickening or jamming, which may be induced by the large velocity gradients arising upon drop impact. In particular, drops of a suspension of nearly hard-core particles in octadecene (volume fraction: approximately 60%) impacting on substrates of different wettability are studied experimentally by high-speed imaging, for impact Weber numbers ranging between 26 and 262. Upon impact, these drops do not exhibit inertial spreading, which is observed for other Newtonian and non-Newtonian fluid drops. On wettable surfaces (glass), impact is followed by capillary-driven spreading at the same rate observed in power-law fluids (Starov's law), while on less wettable surfaces (PTFE) the colloidal suspension drops relax to achieve the shape of a spherical cap, but do not spread. This peculiar impact morphology, and in particular the absence of inertial spreading, is interpreted as a consequence of dilatancy and jamming occurring upon impact.
Original language | English |
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Pages (from-to) | 412-417 |
Number of pages | 6 |
Journal | Powder Technology |
Volume | 270 |
Issue number | Part B |
Early online date | 22 Feb 2014 |
DOIs | |
Publication status | Published - 1 Jan 2015 |
Keywords
- colloidal suspensions
- dilatancy
- drop impact
- hard-sphere interactions
- jamming
- granulation
Fingerprint Dive into the research topics of 'Impact of concentrated colloidal suspension drops on solid surfaces'. Together they form a unique fingerprint.
Profiles
Projects
- 3 Finished
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BTG: New connections in particles and fluids—from fracking and foods, to bacteria and blood
Haw, M., Shipton, Z. K., Zagnoni, M., Oliveira, M., Fletcher, A., Corney, J., Zhang, Y., Pritchard, D. & El Mountassir, G.
1/02/14 → 30/06/14
Project: Internally funded project
Research output
- 7 Citations
- 4 Article
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Does gravity cause load-bearing bridges in colloidal and granular systems?
Jenkins, M. C., Haw, M. D., Barker, G. C., Poon, W. C. K. & Egelhaaf, S. U., 15 Jul 2011, In: Physical Review Letters. 107, 3, 4 p., 038302.Research output: Contribution to journal › Article › peer-review
File16 Citations (Scopus)123 Downloads (Pure) -
Finding bridges in packings of colloidal spheres
Jenkins, M., Haw, M. D., Barker, G., Poon, W. & Egelhaaf, S., 2011, In: Soft Matter. 7, 2, p. 684-690 7 p.Research output: Contribution to journal › Article › peer-review
Open AccessFile13 Citations (Scopus)113 Downloads (Pure) -
Jamming and unjamming of concentrated colloidal dispersions in channel flow
Campbell, A. I. & Haw, M. D., 2010, In: Soft Matter. 6, 19, p. 4688-4693 6 p.Research output: Contribution to journal › Article › peer-review
Open AccessFile24 Citations (Scopus)153 Downloads (Pure)
Activities
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Suspension processing
Mark Haw (Invited speaker)
4 Sep 2012Activity: Participating in or organising an event types › Key-note speaker and plenary lectures at conferences
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'Solidification of colloidal suspensions' international workshop
Mark Haw (Chair)
Sep 2010Activity: Participating in or organising an event types › Organiser of major conference