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  • Open Access

    ARTICLE

    Numerical Simulation of Droplet Breakup, Splitting and Sorting in a Microfluidic Device

    Chekifi. T1,2, Dennai. B1, Khelfaoui. R1

    FDMP-Fluid Dynamics & Materials Processing, Vol.11, No.3, pp. 205-220, 2015, DOI:10.3970/fdmp.2015.011.205

    Abstract Droplet generation, splitting and sorting are investigated numerically in the framework of a VOF technique for interface tracking and a finite-volume numerical method using the commercial code FLUENT. Droplets of water-in-oil are produced by a flow focusing technique relying on the use of a microchannell equipped with an obstacle to split the droplets. The influence of several parameters potentially affecting this process is investigated parametrically towards the end of identifying "optimal" conditions for droplet breakup. Such parameters include surface tension, the capillary number and the main channel width. We show that the capillary number plays a crucial role in determining… More >

  • Open Access

    ARTICLE

    Simulation of Thermal Fluid-structure Interaction Phenomena in a Liquid Sodium Porous System

    Yan Shen1, Hong Zhang1,2,3, Hui Xu1, Tong Bai1, Ping Yu1

    FDMP-Fluid Dynamics & Materials Processing, Vol.10, No.1, pp. 63-81, 2014, DOI:10.3970/fdmp.2014.010.063

    Abstract Single-unit and multi-unit models of porous media (metal felts) have been used to investigate thermal fluid-structure interaction phenomena in a liquid sodium system. Micro-scale aspects have been studied via numerical simulations. The permeability of metal felts has been measured experimentally to verify the reliability of the models used. This integrated approach has allowed a proper evaluation of the interdependencies among phenomena on different scales (including relevant information on skeleton deformation and pressure drop as a function of different parameters). Pressure drop generally increases with velocity and heat flux for both laminar and turbulent flows. The final deformation is greater when… More >

  • Open Access

    ARTICLE

    The Impact of Ink-Jet Droplets on a Paper-Like Structure

    M. Do-Quang1, A. Carlson1, G. Amberg1

    FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.4, pp. 389-402, 2011, DOI:10.3970/fdmp.2011.007.389

    Abstract Inkjet technology has been recognized as one of the most successful and promising micro-system technologies. The wide application areas of printer heads and the increasing demand of high quality prints are making ink consumption and print see-through important topics in the inkjet technology. In the present study we investigate numerically the impact of ink droplets onto a porous material that mimics the paper structure. The mathematical framework is based on a free energy formulation, coupling the Cahn-Hilliard and Navier Stokes equations, for the modelling of the two-phase flow. The case studied here consists of a multiphase flow of air-liquid along… More >

  • Open Access

    ARTICLE

    A Computational Study of High-Speed Droplet Impact

    T. Sanada1, K. Ando2, T. Colonius2

    FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.4, pp. 329-340, 2011, DOI:10.3970/fdmp.2011.007.329

    Abstract When a droplet impacts a solid surface at high speed, the contact periphery expands very quickly and liquid compressibility plays an important role in the initial dynamics and the formation of lateral jets. The high speed impact results in high pressures that can account for the surface erosion. In this study, we numerically investigated a high speed droplet impacts on a solid wall. The multicomponent Euler equations with the stiffened equation of state are computed using a FV-WENO scheme with an HLLC Riemann solver that accurately captures shocks and interfaces. In order to compare the available theories and experiments, 1D,… More >

  • Open Access

    ARTICLE

    Viscoelastic Drop Deformation in a Micro-Contraction

    Malcolm R. Davidson1, Dalton J.E. Harvie1

    FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.3, pp. 317-328, 2011, DOI:10.3970/fdmp.2011.007.317

    Abstract A volume-of-fluid numerical method, adapted by the authors [Harvie, Cooper-White and Davidson (2008)] to simulate the flow of viscoelastic fluids, is used to predict deformation of a viscoelastic droplet carried by an immiscible Newtonian liquid through an axisymmetric microfluidic contraction-expansion. Values of the capillary number and elasticity number are chosen based on corresponding values for a rectangular contraction for which a reentrant cavity at the rear of the drop and subsequent encapsulation behaviour was observed experimentally by Harvie, Cooper-White and Davidson (2008). A reentrant cavity, similar to the observed one, is predicted; however, encapsulation is not achieved. Unexpectedly, a narrow… More >

  • Open Access

    ARTICLE

    Binary Collisions of Immiscible Liquid Drops for Liquid Encapsulation

    Carole Planchette1, Elise Lorenceau1, Günter Brenn2

    FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.3, pp. 279-302, 2011, DOI:10.3970/fdmp.2011.007.279

    Abstract This work is dedicated to a general description of collisions between two drops of immiscible liquids. Our approach is mainly experimental and allows us to describe the outcomes of such collisions according to a set of relevant parameters. Varying the relative velocity U as well as the impact parameter X we can build for each pair of investigated liquids a nomogram X,U showing three possible regimes: coalescence, head-on separation and off-center separation. In this paper, we also study the influence of the liquid properties, i.e. viscosity, density, surface and interfacial tensions using a set of aqueous glycerol solutions together with… More >

  • Open Access

    ARTICLE

    Numerical Simulation of an Axisymmetric Compound Droplet by Three-Fluid Front-Tracking Method

    S. Homma1, M. Yokotsuka1, T. Tanaka1, K. Moriguchi1, J. Koga1, G. Tryggvason2

    FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.3, pp. 231-240, 2011, DOI:10.3970/fdmp.2011.007.231

    Abstract We develop a three-fluid front-tracking method in order to simulate the motion of an axisymmetry compound droplet, which consists of three immiscible fluids separated by two different interfaces. The two interfaces of the compound droplet are represented by two different sets of the front-tracking elements immersed on the Eulerian grid mesh, where the velocities and the pressure are calculated. The density and viscosity profiles with jumps at the interfaces are successfully determined from the location and the connection information of the front-tracking elements. The motion of a compound droplet is simulated on axisymmetric cylindrical coordinates. The results show that the… More >

  • Open Access

    ARTICLE

    Droplet Behavior within an LPP Ambiance

    M. Chrigui1,2, L. Schneider1, A. Zghal2, A. Sadiki1, J. Janicka1

    FDMP-Fluid Dynamics & Materials Processing, Vol.6, No.4, pp. 399-408, 2010, DOI:10.3970/fdmp.2010.006.399

    Abstract This paper deals with the numerical simulation of droplet dispersion and evaporation within an LPP (Lean Premix Prevaporized) burner. The Eulerian-Lagrangian approach was used for this purpose, and a fully two way-coupling was accounted for. For the phase transition, a non-equilibrium evaporation model was applied that differs strongly from the equilibrium one where there are high evaporation rates. The non-equilibrium conditions were fulfilled in the investigated configuration, as the droplets at the inlet had a mean diameter of 50mm. The numerical results of water droplet velocities, corresponding fluctuations, and diameters were compared with experimental data. Good agreement was found. More >

  • Open Access

    ARTICLE

    A Phase Field Description of Spatio-Temporal Behavior in Thin Liquid Layers

    Rodica Borcia1, Michael Bestehorn2

    FDMP-Fluid Dynamics & Materials Processing, Vol.6, No.1, pp. 1-12, 2010, DOI:10.3970/fdmp.2010.006.001

    Abstract We study numerically the fully nonlinear evolution of thin liquid films on solid supports in three spatial dimensions. A phase field model is used as mathematical tool. Homogeneous and inhomogeneous substrates are taken into account. For flat homogeneous substrates the stability of thin liquid layers is investigated under the action of gravity. The coarsening process at the solid boundary can be controlled on inhomogeneous substrates. On substrates chemically patterned in an adequate way with hydrophobic and hydrophilic spots (functional surfaces), one can obtain stable regular liquid droplets as final dewetted morphology. More >

  • Open Access

    ARTICLE

    Liquid Droplet Impact onto Flat and Rigid Surfaces: Initial Ejection Velocity of the Lamella

    Davood Kalantari1

    FDMP-Fluid Dynamics & Materials Processing, Vol.5, No.1, pp. 81-92, 2009, DOI:10.3970/fdmp.2009.005.081

    Abstract In this paper a theoretical approach is elaborated for modelling the impact and ensuing spreading behaviour of a liquid droplet after its collision with a flat and rigid surface. The major outcomes of such a study can be summarized as follows: 1) The propagating-shock-wave velocity associated with the droplet is not a constant value but depends on the impact velocity and the physical and geometrical properties of the droplet. 2) The initial radial ejection velocity of the lamella is proportional to the shock-wave velocity (ua) and the impact velocity (0) according to the expression (a-u0)1/2. 3) The deceleration behaviour of… More >

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