Dr Alexander Wray

Wray AW, Matar OK, Craster, Sefiane K, Papageorgiou DTet al., 2015, Electrostatic Suppression of the "Coffee-stain Effect", Procedia IUTAM, Vol: 15, Pages: 172-177, ISSN: 2210-9838

The dynamics of a slender, nano-particle laden droplet are examined when it is subjected to an electric field. Under a long-waveassumption, the governing equations are reduced to a coupled pair of nonlinear evolution equations prescribing the dynamics of theinterface and the depth-averaged particle concentration. This incorporates the effects of viscous stress, capillarity, electrostaticallyinducedMaxwell stress, van der Waals forces, evaporation and concentration-dependent rheology. It has previously been shown27that electric fields can be used to suppress the ring effect typically exhibited when such a droplet undergoes evaporation. Wedemonstrate here that the use of electric fields affords many diverse ways of controlling the droplets.

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Wray AW, Papageorgiou DT, Craster RV, Sefiane K, Matar OKet al., 2014, Electrostatic Suppression of the "Coffee Stain Effect", LANGMUIR, Vol: 30, Pages: 5849-5858, ISSN: 0743-7463

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• Citations: 49

Wray AW, Papageorgiou DT, Matar OK, 2013, Electrostatically controlled large-amplitude, non-axisymmetric waves in thin film flows down a cylinder, Journal of Fluid Mechanics, Vol: 736, ISSN: 1469-7645

We examine the dynamics of a thin film flowing under gravity down the exterior of a vertically aligned inner cylinder, with a co-aligned, concentric cylinder acting as an outer electrode; the space between the outer cylinder and the film is occupied by an inviscid gas. The stability of the interface is studied when it is subjected to an electric field, applied by imposing a potential difference between the two cylinders. Leaky-dielectric theory is used in conjunction with asymptotic reduction, in the large-conductivity limit, to derive a single, two-dimensional evolution equation for the interfacial location, which accounts for gravity, capillarity, and electrostatic effects. A linear stability analysis is carried out which shows that non-axisymmetric modes become more dominant with increasing electric field strength. Our fully two-dimensional numerical solutions of the evolution equation demonstrate qualitative agreement between the trends observed in the nonlinear regime and those predicted by linear theory. These numerical solutions also show that, depending on the electric field strength and the relative proximity of the outer electrode, the interface either remains spatially uniform, or exhibits either axisymmetric or, importantly, non-axisymmetric travelling waves. The effect of wave formation on the interfacial area is investigated in connection with the use of electric fields to control thin film flows to enhance heat and mass transfer rates.

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Wray AW, Papageorgiou DT, Matar OK, 2013, Electrified coating flows on vertical fibres: enhancement or suppression of interfacial dynamics, JOURNAL OF FLUID MECHANICS, Vol: 735, Pages: 427-456, ISSN: 0022-1120

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• Citations: 13

Wray AW, Matar O, Papageorgiou DT, 2012, Non-linear waves in electrified viscous film flow down a vertical cylinder, IMA JOURNAL OF APPLIED MATHEMATICS, Vol: 77, Pages: 430-440, ISSN: 0272-4960

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• Citations: 16