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  • Open Access

    ARTICLE

    Mesoscopic Simulation of Binary Immiscible Fluids Flow in a Square Microchannel with Hydrophobic Surfaces

    S. Chen1,2, Y. Liu1,3, B.C. Khoo4, X.J. Fan5, J.T. Fan6

    CMES-Computer Modeling in Engineering & Sciences, Vol.19, No.3, pp. 181-196, 2007, DOI:10.3970/cmes.2007.019.181

    Abstract The mesoscopic simulation for fluids flow in a square microchannel is investigated using dissipative particle dynamics. The velocity distribution for single fluid in a square channel is compared with the solutions of CFD solver, which is found to be in good agreement with each other. The no-slip boundary condition could be well held for the repulsive coefficient ranged from 9.68 to 18.0. For the same range of repulsive coefficient, various wettabilities could be obtained by changing the repulsive coefficient for binary immiscible fluids, in which the immiscible fluids are achieved by increasing the repulsive force… More >

  • Open Access

    ARTICLE

    Modeling the Wetting Effects in Droplet Impingement using Particle Method

    Heng Xie1, Seiichi Koshizuka2, Yoshiaki Oka2

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.1, pp. 1-16, 2007, DOI:10.3970/cmes.2007.018.001

    Abstract A model of a single liquid drop colliding on solid surface is developed based with Moving Particle Semi-implicit (MPS) method. The mathematical model involves gravity, viscosity and surface tension. The wettability between the impact liquid and the solid surface is modeled by the contact angle model and the non-slip boundary condition. The particles of the drop are divided into four types in which the model varies to simulate the liquid particles in different area. The model is validated by the comparison of the theoretical results. The complete dynamic process including the spreading, the recoiling, re-bouncing More >

  • Open Access

    ARTICLE

    Phase field models and Marangoni flows

    Rodica Borcia1,2, Michael Bestehorn2

    FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.4, pp. 287-294, 2007, DOI:10.3970/fdmp.2007.003.287

    Abstract We developed a phase field model for Marangoni convection in compressible fluids of van der Waals type far from criticality. The theoretical description is based on the Navier-Stokes equation with extra terms responsible for describing the Marangoni effect, the classical heat equation, and the continuity equation. The model previously developed for a two-layer geometry is now extended to drops and bubbles. Finally, we report on 2D numerical simulations for drop Marangoni migration in a vertical temperature gradient. More >

  • Open Access

    ARTICLE

    Improvements for calculating two-phase bubble and drop motion using an adaptive sharp interface method.

    Mark Sussman1, Mitsuhiro Ohta2

    FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.1, pp. 21-36, 2007, DOI:10.3970/fdmp.2007.003.021

    Abstract In this paper, we describe new techniques for numerically approximating two-phase flows. Specifically, we present new techniques for treating the viscosity and surface tension terms that appear in the Navier-Stokes equations for incompressible two-phase flow. Our resulting numerical method has the property that results computed using our two-phase algorithm approach the corresponding "one-phase'' algorithm in the limit of zero gas density/viscosity; i.e. the two-phase results approach the one-phase free-boundary results in the limit that the gas is assumed to become a uniform pressure void. By grid convergence checks and comparison with previous experimental data, we More >

  • Open Access

    ARTICLE

    Surface Phase Separation and Flow in a Simple Model of Multicomponent Drops and Vesicles

    J.S. Lowengrub1, J-J. Xu2, A. Voigt3

    FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.1, pp. 1-20, 2007, DOI:10.3970/fdmp.2007.003.001

    Abstract We introduce and investigate numerically a thermodynamically consistent simple model of a drop or vesicle in which the interfacial surface contains multiple constitutive components (e.g. amphiphilic molecules). The model describes the nonlinear coupling among the flow, drop/vesicle morphology and the evolution of the surface phases. We consider a highly simplified version of the Helfrich model for fluid-like vesicle membranes in which we neglect the effects of bending forces and spontaneous curvature but keep the effects of inhomogeneous surface tension forces. Thus, this model may also describe liquid drops. To solve the highly nonlinear, coupled system More >

  • Open Access

    ARTICLE

    Novel Engineered Nanocrystalline Ultra-hydrophilic Hard Ceramic Coatings for Attachment and Growth of Bone Marrow Stromal Cells

    F. Namavar1, J. D. Jackson2, J. G. Sharp3, S. Varma1, H. Haider1, C. Feschuk1, K. L. Garvin1

    Molecular & Cellular Biomechanics, Vol.3, No.4, pp. 171-172, 2006, DOI:10.32604/mcb.2006.003.171

    Abstract This article has no abstract. 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

    On the Dynamic Capillary Effects in the Wetting and evaporation process of Binary Droplets

    K. Sefiane1

    FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.3, pp. 267-276, 2005, DOI:10.3970/fdmp.2005.001.267

    Abstract In this paper the experimental results on the wetting behaviour of volatile binary sessile drops are reported. The evaporation rate is varied through the control of the ambient total pressure. The dynamic wetting contact angle of an evaporating Water-Ethanol drop is investigated at various sub-atmospheric pressures. The wetting properties (contact angle, shape and volume) are monitored in time using a drop shape analysis instrument. The results show that the evaporation of the binary droplet takes place in two stages: the first stage where the wetting behaviour is very similar to the pure ethanol case and… More >

  • Open Access

    ARTICLE

    Locomotion of a Viscous Drop, Induced by the Internal Secretion of Surfactant: Boundary Effects

    O.M. Lavrenteva1, D. Tsemakh, A. Nir

    FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.2, pp. 131-152, 2005, DOI:10.3970/fdmp.2005.001.131

    Abstract We have studied the motion of a drop, induced by the internal secretion of a surface-active substance, in the vicinity of solid walls or non-deformable liquid-liquid interface under micro-gravity conditions. The secreted substance renders a non-uniform distribution of surfactant along the outer surface that, in turn, results in interfacial stress variation that ultimately leads to a surface motion and to locomotion of the drop. Cases of plane and spherical boundaries have been considered as well as cases of linear and non-linear dependence of the interfacial tension on concentration of surfactant. The dependence of the drop More >

  • Open Access

    ARTICLE

    Assessment of VOF Strategies for the Analysis of Marangoni Migration, Collisional Coagulation of Droplets and Thermal Wake Effects in Metal Alloys Under Microgravity Conditions

    Marcello Lappa 1

    CMC-Computers, Materials & Continua, Vol.2, No.1, pp. 51-64, 2005, DOI:10.3970/cmc.2005.002.051

    Abstract A possible approach for the investigation of a number of aspects related to the processing of immiscible alloys, made possible by recent progress in both fields of moving boundary (VOF) methods and speed of computers, is discussed. It can capture in a single numerical treatment and without limiting assumptions both macroscopic information (i.e. the macrophysical problem, heretofore treated in terms of population dynamics) and microscopic details (i.e. the microphysical problem, heretofore treated within the framework of boundary integral methods and/or under the assumption of nondeformable drops). The role played by coalescence in changing the Marangoni More >

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