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  • Journal article
    Kahouadji L, Périnet N, Tuckerman LS, Shin S, Chergui J, Juric Det al., 2015,

    Numerical simulation of super-square patterns in Faraday waves

    , Journal of Fluid Mechanics, ISSN: 1469-7645

    We report the first simulations of the Faraday instability using the full three-dimensional Navier–Stokes equations in domains much larger than the characteristic wavelength of the pattern. We use a massively parallel code based on a hybrid front-tracking/level-set algorithm for Lagrangian tracking of arbitrarily deformable phase interfaces. Simulations performed in square and cylindrical domains yield complex patterns. In particular, a superlattice-like pattern similar to those of Douady & Fauve (Europhys. Lett., vol. 6, 1988, pp. 221–226) and Douady (J. Fluid Mech., vol. 221, 1990, pp. 383–409) is observed. The pattern consists of the superposition of two square superlattices. We conjecture that such patterns are widespread if the square container is large compared with the critical wavelength. In the cylinder, pentagonal cells near the outer wall allow a square-wave pattern to be accommodated in the centre.

  • Journal article
    Saenz PJ, Sefiane K, Kim J, Matar OK, Valluri Pet al., 2015,

    Evaporation of sessile drops: a three-dimensional approach

    , Journal of Fluid Mechanics, Vol: 772, Pages: 705-739, ISSN: 1469-7645

    The evaporation of non-axisymmetric sessile drops is studied by means of experiments and three-dimensional direct numerical simulations (DNS). The emergence of azimuthal currents and pairs of counter-rotating vortices in the liquid bulk flow is reported in drops with non-circular contact area. These phenomena, especially the latter, which is also observed experimentally, are found to play a critical role in the transient flow dynamics and associated heat transfer. Non-circular drops exhibit variable wettability along the pinned contact line sensitive to the choice of system parameters, and inversely dependent on the local contact-line curvature, providing a simple criterion for estimating the approximate contact-angle distribution. The evaporation rate is found to vary in the same order of magnitude as the liquid–gas interfacial area. Furthermore, the more complex case of drops evaporating with a moving contact line (MCL) in the constant contact-angle mode is addressed. Interestingly, the numerical results demonstrate that the average interface temperature remains essentially constant as the drop evaporates in the constant-angle (CA) mode, while this increases in the constant-radius (CR) mode as the drops become thinner. It is therefore concluded that, for increasing substrate heating, the evaporation rate increases more rapidly in the CR mode than in the CA mode. In other words, the higher the temperature the larger the difference between the lifetimes of an evaporating drop in the CA mode with respect to that evaporating in the CR mode.

  • Journal article
    May EF, Tay WJ, Nania M, Aleji A, Al-Ghafri S, Trusler JPMet al., 2015,

    Erratum: “Physical apparatus parameters and model for vibrating tube densimeters at pressures to 140 MPa and temperatures to 473 K” [Rev. Sci. Instrum. 85, 095111 (2014)]

    , Review of Scientific Instruments, Vol: 86, ISSN: 1089-7623
  • Journal article
    Smith ER, Heyes DM, Dini D, Zaki TAet al., 2015,

    A localized momentum constraint for non-equilibrium molecular dynamics simulations

    , JOURNAL OF CHEMICAL PHYSICS, Vol: 142, ISSN: 0021-9606
  • Journal article
    Nania M, Matar OK, Cabral JT, 2015,

    Frontal vitrification of PDMS using air plasma and consequences for surface wrinkling

    , Soft Matter, Vol: 11, Pages: 3067-3075, ISSN: 1744-6848

    We study the surface oxidation of polydimethylsiloxane (PDMS) by air plasma exposure and its implications for the mechanically-induced surface wrinkling of the resulting glass–elastomer bilayers. The effect of plasma frequency (kHz and MHz), oxygen content (from O2 to air), pressure (0.5 ≤ P ≤ 1.5 mbar), as well as exposure time and power, is quantified in terms of the resulting glassy skin thickness h, inferred from wrinkling experiments. The glassy skin thickness is found to increase logarithmically with an exposure time t, for different induction powers p, and all data collapse in terms of a plasma dose, D ≡ p × t. The kinetics of film propagation are found to increase with the oxygen molar fraction yO2 and decrease with the gas pressure P, allowing both the wrinkling wavelength λ and amplitude A to be effectively controlled by gas pressure and composition. A generalised relationship for frontal vitrification is obtained by re-scaling all λ and h data by D/P. A coarse-grained wave propagation model effectively describes and quantifies the process stages (induction, skin formation and propagation) under all the conditions studied. Equipped with this knowledge, we further expand the capabilities of plasma oxidation for PDMS wrinkling, and a wavelength of λ ≈ 100 nm is readily attained with a modest strain εprestrain ≈ 20%.

  • Journal article
    Theodorakis PE, Mueller EA, Craster RV, Matar OKet al., 2015,

    Superspreading: Mechanisms and Molecular Design

    , Langmuir, Vol: 31, Pages: 2304-2309, ISSN: 1520-5827
  • Conference paper
    Angeli P, Azzopardi BJ, Hewakandamby B, Hewitt GF, Pain CC, Simmons MJH, Matar OKet al., 2015,

    Multi-scale exploration of multiphase physics in flows (MEMPHIS): A framework for the next-generation predictive tools for multiphase flows

    , Pages: 242-249

    Ins this paper, we outline the framework that we are developing as part of the Multi-scale Exploration of Multiphase PHysIcs in flowS (MEMPHIS) programme to create the next generation modelling tools for complex multiphase flows. These flows are of central importance to micro-fluidics, oil-and-gas, nuclear, and biomedical applications, and every processing and manufacturing technology. This framework involves the establishment of a transparent linkage between input and prediction to allow systematic error-source identification, and, optimal, model-driven experimentation, to maximise prediction accuracy. The framework also involves massively-parallelisable numerical methods, capable of running efficiently on 105-106 core supercomputers, with optimally-adaptive, three-dimensional resolution, and sophisticated multi-scale physical models. The overall aim of this framework is to provide unprecedented resolution of multi-scale, multiphase phenomena, thereby minimising the reliance on correlations and empiricism.

  • Conference paper
    Yang J, Tajudin ZB, Coletti F, Muller A, MacChietto S, Matar OKet al., 2015,

    Numerical simulation of fouling in crude-oil heat exchangers: The interaction between different fouling routes

    , Pages: 833-842
  • Journal article
    Tripathi MK, Sahu KC, Karapetsas G, Sefiane K, Matar OKet al., 2015,

    Non-isothermal bubble rise: non-monotonic dependence of surface tension on temperature

    , JOURNAL OF FLUID MECHANICS, Vol: 763, Pages: 82-108, ISSN: 0022-1120
  • Journal article
    Swain PAP, Karapetsas G, Matar OK, Sahu KCet al., 2015,

    Numerical simulation of pressure-driven displacement of a viscoplastic material by a Newtonian fluid using the lattice Boltzmann method

    , EUROPEAN JOURNAL OF MECHANICS B-FLUIDS, Vol: 49, Pages: 197-207, ISSN: 0997-7546

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