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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

    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

    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

    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 >

  • Open Access

    ARTICLE

    Electromagnetic Levitation Part III: Thermophysical Property Measurements in Microgravity

    Sayavur I. Bakhtiyarov1, Dennis A. Siginer2

    FDMP-Fluid Dynamics & Materials Processing, Vol.5, No.1, pp. 1-22, 2009, DOI:10.3970/fdmp.2009.005.001

    Abstract Strong inhomogeneous magnetic fields are necessary to generate a finite levitation force in ground based electromagnetic levitation techniques. External forces such as magnetic and gravitational forces influence the oscillation spectrum and counteract the surface movement resulting in a frequency shift, and making the use of electromagnetic levitation techniques in microgravity an attractive alternative to measure thermophysical properties of liquid metals. Under microgravity conditions the magnetic field strength around a liquid droplet is significantly lower than that required to position the same specimen against earth gravity. Hence, a low magnetic field strength results in a low amount of heat energy absorbed… More >

  • Open Access

    ARTICLE

    Precursor Film Length Ahead Droplet Traveling on Solid Substrate

    I. Ueno1, T. Konisho2, T. Kawase3, T. Watanabe4

    FDMP-Fluid Dynamics & Materials Processing, Vol.4, No.1, pp. 21-26, 2008, DOI:10.3970/fdmp.2008.004.021

    Abstract The present authors carried out an experimental study with a special interest upon the dynamics of the fluid in the vicinity of the boundary line of three phases; solid-liquid-gas interface, which is so-called `contact line.' The moving droplet on the solid substrate is accompanied with the movement of the boundary line of three phases; solid-liquid-gas interface, which is so-called macroscopic 'contact line.' Existing studies have indicated there is a thin liquid film known as 'precursor film' ahead the contact line of the droplet. In the present study the precursor film was detected by applying conventional ellipsometer, and its existing length… More >

  • Open Access

    ARTICLE

    Scalings for Droplet Sizes in Shear-Driven Breakup: Non-Microfluidic Ways to Monodisperse Emulsions

    V. Cristini1, Y. Renardy2

    FDMP-Fluid Dynamics & Materials Processing, Vol.2, No.2, pp. 77-94, 2006, DOI:10.3970/fdmp.2006.002.077

    Abstract We review studies of a drop of viscous liquid, suspended in another liquid, and undergoing breakup in an impulsively started shear flow. Stokes flow conditions as well as the effects of inertia are reported. They reveal a universal scaling for the fragments, which allows one to use sheared emulsions to produce monodispersity as an alternative to microfluidic devices. More >

  • Open Access

    ARTICLE

    Evaluation of some of the existing models for droplet and spray/wall interactions

    Davood Kalantari1

    FDMP-Fluid Dynamics & Materials Processing, Vol.9, No.2, pp. 169-182, 2013, DOI:10.3970/fdmp.2013.009.169

    Abstract In this study, a critical summary of existing spray/wall interaction models is given in synergy with a review of available experimental data. In particular, special attention is devoted to the limitations, difficulties and complexities of the most used approaches in the literatures. An attempt is also made to indicate the bottlenecks and criticalities which typically arise when investigators try to extend results obtained for isolated droplets to the more complex dynamics produced by spray impacts. More >

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