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  • Open Access

    ARTICLE

    A Unified Approach to Numerical Modeling of Fully and Partially Saturated Porous Materials by Considering Air Dissolved in Water

    D. Gawin1, L. Sanavia2

    CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.3, pp. 255-302, 2009, DOI:10.3970/cmes.2009.053.255

    Abstract This paper presents a unified mathematical approach to model the hydro-thermo-mechanical behavior of saturated and partially saturated porous media by considering the effects of air dissolved in liquid water. The model equations are discretized by means of the Finite Element method. A correspondingly updated code is used to analyze two examples; the first one is the well known Liakopoulos test, i.e. the drainage of liquid water from a 1m column of sand, which is used to validate numerically the model here developed. As second example, a biaxial compression test of undrained dense sands where cavitation More >

  • Open Access

    ARTICLE

    Molecular Dynamics Analysis of the Instability for a Nano-Scale Liquid Thread

    Chun-Lang Yeh 1

    CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.3, pp. 253-284, 2009, DOI:10.3970/cmes.2009.050.253

    Abstract This paper investigates the instability of a liquid thread by molecular dynamics (MD) simulation. The influences of liquid thread radius, fundamental cell length, and temperature are discussed. Snapshots of molecules, number of liquid particles formed, and density field are analyzed. Two linear stability criteria, namely Rayleigh's stability criterion and Kim's stability criterion, are accessed for their validity in molecular scale. It is found that a liquid thread is more unstable and produces more liquid particles in the fundamental cell when it is thinner or at a higher temperature. In addition, a liquid thread with a More >

  • Open Access

    ARTICLE

    Numerical Solution of 2D Natural Convection in a Concentric Annulus with Solid-Liquid Phase Change

    R. Avila1, F.J. Solorio1

    CMES-Computer Modeling in Engineering & Sciences, Vol.44, No.2, pp. 177-202, 2009, DOI:10.3970/cmes.2009.044.177

    Abstract Heat transfer processes involving phase change either, solidification or melting, appear frequently in nature and in industrial applications. In this paper the convective patterns that arise from a 2D shear driven annular flow (without and with melting), are presented. The convective annular flow with radial gravity can be considered as a simplified model of the atmospheric flow in the terrestrial equatorial plane (bounded by the warm surface of the Earth and the cold tropopause). The governing equations have been numerically solved by the Spectral Element Method. The numerical results reported in this paper, for the… More >

  • Open Access

    ARTICLE

    Numerical Simulation of Three Dimensional Low Prandtl Liquid Flow in a Parallelepiped Cavity Under an external Magnetic Field

    F. Mechighel1,2, M. El Ganaoui1, M. Kadja2, B. Pateyron3, S. Dost4

    FDMP-Fluid Dynamics & Materials Processing, Vol.5, No.4, pp. 313-330, 2009, DOI:10.3970/fdmp.2009.005.313

    Abstract A numerical study has been carried out to investigate the three-dimen -sional buoyant flow in a parallelepiped box heated from below and partially from the two sidewalls (a configuration commonly used for solidification problems and crystal growth systems). Attention has been paid, in particular, to phenomena of symmetry breaking and transition to unsteady non-symmetric convection for a low Prandtl number fluid (Pr=0.01). The influence of an applied horizontal magnetic field on the stability properties of the flow has been also considered. Results obtained may be summarized as follows: In the absence of magnetic field and 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. More >

  • Open Access

    ARTICLE

    Nanobubbles at Water-Solid Interfaces: Calculation of the Contact Angle Based on a Simple Model

    H. Elnaiem1, D. Casimir1, P. Misra1, S.M. Gatica1,2

    CMC-Computers, Materials & Continua, Vol.14, No.1, pp. 23-34, 2009, DOI:10.3970/cmc.2009.014.023

    Abstract Nanobubbles have been found to form at the interface of water and solid surfaces. We examine the conditions for such bubbles to form and estimate the pressure inside the bubble based on thermodynamic considerations. Using a simple model we calculate the contact angle for a wide range of temperatures and hypothetical substrates possessing a continuous range of strengths. We show that as the temperature increases the shape of a bubble changes continuously from a spherical cap with low curvature to a complete sphere. An equivalent effect results from either increasing the strength of the solid More >

  • Open Access

    ARTICLE

    Modelling of Evaporative Cooling of Porous Medium Filled with Evaporative Liquid

    D.P.Mondal1, S.Das1, Anshul Badkul1, Nidhi Jha1

    CMC-Computers, Materials & Continua, Vol.13, No.2, pp. 115-134, 2009, DOI:10.3970/cmc.2009.013.115

    Abstract The cooling effect by evaporative liquid is modeled by considering that heat is transferred from the system to the surrounding due to evaporation of liquid through the pores present in the medium. The variation of cooling rate with cell size, volume fraction of pores and physical conditions has been analyzed. The model demonstrates that it increases with increase in thickness of the foam slab and with increase in velocity of air. It is also observed that cooling effect decreases with decrease in volume fraction of porosity and with increase in relative density, cell size, thermal More >

  • Open Access

    ARTICLE

    A cryopreservation protocol for immature zygotic embryos of species of Ilex (Aquifoliaceae)

    LUIS A. MROGINSKI*, PEDRO A. SANSBERRO, ADRIANA M. SCOCCHI, CLAUDIA LUNA, HEBE Y. REY

    BIOCELL, Vol.32, No.1, pp. 33-39, 2008, DOI:10.32604/biocell.2008.32.033

    Abstract Tropical Ilex species have recalcitrant seeds. This work describes experiments demonstrating the feasibility of long-term conservation of Ilex brasiliensis, I. brevicuspis, I. dumosa, I. intergerrima, I. paraguariensis, I. pseudoboxus, I. taubertiana, and I. theezans through cryopreservation of zygotic rudimentary embryos at the heart developmental stage. The embryos were aseptically removed from the seeds and precultured (7 days) in the dark, at 27± 2ºC on solidified (0.8% agar) 1/4MS medium, [consisting of quarterstrength salts and vitamins of Murashige and Skoog (1962) medium] with 3% sucrose and 0.1 mg/l Zeatin. The embryos were then encapsulated in 3% calcium alginate beads… More >

  • Open Access

    ABSTRACT

    Numerical Investigation on Resonant Sloshing Characteristics of 2-D Baffled Liquid Container

    Jong-Kook Cha1, Jin-Rae Cho1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.7, No.3, pp. 129-134, 2008, DOI:10.3970/icces.2008.007.129

    Abstract Sloshing flow is formulated based on the linearized potential flow theory, while an artificial damping term is employed into the kinematic free-surface condition to reflect the eminent dissipation effect in resonant sloshing. Through the numerical analysis of sloshing frequency response with respect to the number, location and opening width of baffle, the sloshing damping characteristics by baffle are parametrically investigated. More >

  • Open Access

    ARTICLE

    The Concept of a Vibrational Cell for Studying the Interface Chemical Kinetics. Vibrational Flow Structure

    A.A. Ivanova1, V.G. Kozlov1,2,3, D.A. Polezhaev1, D. Pareau3, M. Stambouli3

    FDMP-Fluid Dynamics & Materials Processing, Vol.4, No.3, pp. 211-220, 2008, DOI:10.3970/fdmp.2008.004.211

    Abstract The problem for the optimization of mass-transfer on the interface of two immiscible liquids by means of vibrational hydromechanics is studied experimentally. A new vibrational cell of Lewis's type expressly conceived for such purposes is described. Flow is generated by activators in the form of disks inducing translational axial oscillations near the opposite end faces of the cavity. It is shown that such vibrating disks can lead to the onset of a large-scale toroidal whirlwind effectively mixing the liquid throughout the volume. According to the experiments, in particular, axisymmetrical radial flows are generated on both More >

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