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  • Open Access

    ARTICLE

    How Does Buoyancy-driven Convection Affect Biological Macromolecular Crystallization? An Analysis of Microgravity and Hypergravity Effects by Means of Magnetic Field Gradients

    N.I. Wakayama1, D.C. Yin2, J.W. Qi3

    FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.2, pp. 153-170, 2005, DOI:10.3970/fdmp.2005.001.153

    Abstract The production of crystals of adequate size and high quality is the "bottleneck'' for three-dimensional structure analysis of protein crystals. In this work, in order to shed additional light on the (still controversial) beneficial effect of microgravity on crystal growth, we focus on recent advanced experimental and theoretical research about the effects of buoyancy-driven convection on protein crystallization. In the light of the numerical studies the following major outcomes can be highlighted: (1) when the crystal size exceeds several dozens of µm, buoyancy-driven convection dominates solute transport near the growing crystal and the crystal growth rate… 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

    Implementation of the level set method for continuum mechanics based tumor growth models

    Cosmina S. Hogea1, Bruce T. Murray1, James A. Sethian2,3

    FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.2, pp. 109-130, 2005, DOI:10.3970/fdmp.2005.001.109

    Abstract A computational framework for simulating growth and transport in biological materials based on continuum models is proposed. The advantages of the finite difference methodology employed are generality and relative simplicity of implementation. The Cartesian mesh/level set method developed here provides a computational tool for the investigation of a host of transport-based tissue/tumor growth models, that are posed as free or moving boundary problems and may exhibit complicated boundary evolution including topological changes. The methodology is tested here on a widely studied "incompressible flow" type tumor growth model with a numerical implementation in two dimensions; comparisons More >

  • Open Access

    ARTICLE

    A Computational Study of Bubble Motion in Newtonian and Viscoelastic Fluids

    Edwin Jim ´enez1, Mark Sussman2, Mitsuhiro Ohta3

    FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.2, pp. 97-108, 2005, DOI:10.3970/fdmp.2005.001.097

    Abstract The aim of this paper is to utilize a numerical model to compute bubble motion in quiescent Newtonian and viscoelastic liquids. For our numerical method, we use a coupled level set and volume-of-fluid method with a second order treatment for the jump conditions related to surface tension. We investigate axisymmetric gas-liquid systems with large density and viscosity ratios as well as buoyancy-driven flows with complex changes in topology. We present comparisons to previous computational results as well as experimental results. More >

  • Open Access

    ARTICLE

    Thermocapillary Flow and Phase Change in Some Widespread Materials Processes

    Gustav Amberg1, Junichiro Shiomi2

    FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 81-96, 2005, DOI:10.3970/fdmp.2005.001.081

    Abstract A few issues in materials science are reviewed with regard to the importance of fluid flows. The effect of convection on generic solidification problems is discussed. One relevant class of flows in melts is those driven by surface tension gradients. In welding this thermo- or solutocapillary flow will determine the penetration depth, and will depend very sensitively on the composition of the material, through the dependence of surface tension on temperature, presence of surfactants, etc. In crystal growth the convective motion in the melt may cause instabilities that are often undesired in practical processes. The More >

  • Open Access

    ARTICLE

    Phase Distribution of Bubbly Flows under Terrestrial and Microgravity Conditions

    Asghar Esmaeeli1

    FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 63-80, 2005, DOI:10.3970/fdmp.2005.001.063

    Abstract We use direct numerical simulations to study phase distribution of bubbles under terrestrial and microgravity conditions. The full Navier-Stokes and energy equations, for the flows inside and outside the bubbles, are solved using a front tracking/finite difference technique. Both nearly spherical and deformable bubbles are considered. For buoyancy-driven flows, spherical bubbles at Re = O(10) and deformable ones at Re = O(100) exhibit a uniform spatial distribution at quasi steady-state conditions, while nearly spherical bubbles at Re = O(100) form horizontal rafts. Bubbles, driven by thermocapillary effects in microgravity, also form horizontal rafts, but due to an More >

  • Open Access

    ARTICLE

    Numerical Simulation of CZ Crystal Growth of Oxide

    T. Tsukada1, M. Kobayashi2, C. J. Jing3, N. Imaishi4

    FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 45-62, 2005, DOI:10.3970/fdmp.2005.001.045

    Abstract In this paper, our recent numerical studies on the Czochralski (CZ) crystal growth of oxide are surveyed. In the first part of the analysis, a "global" heat transfer model for an inductively heated CZ furnace is introduced and depicted in detail. It is emphasized that accounting for the internal radiation within the crystal and/or melt is of crucial importance since they are often semitransparent to infrared radiation. Results coming from such a "global" approach suggest that the melt/crystal interface shape is strongly affected by the optical properties of the crystal, of the melt and by More >

  • Open Access

    ARTICLE

    Effects of Rotation on Heat Flow, Segregation, and Zone Shape in a Small-scale Floating-zone Silicon Growth under Axial and Transversal Magnetic Fields

    C. W. Lan1, B. C. Yeh

    FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 33-44, 2005, DOI:10.3970/fdmp.2005.001.033

    Abstract The suppression of unstable Marangoni convection in floating-zone crystal growth by magnetic fields has enjoyed over recent years a widespread use as a reliable and useful strategy. A transversal direction of the field is particularly efficient, but asymmetric zone shapes and thus segregation are induced. Counter-rotation of the feed and of the crystal rods is a common way to improve dopant homogeneity. However, its effects under magnetic fields are complex and have not yet been studied in detail. In the present analysis, three-dimensional (3D) simulations based on a finite-volume/multigrid method are used to illustrate the More >

  • Open Access

    ARTICLE

    On the Three-Dimensional Instability of Thermocapillary Convection in Arbitrarily Heated Floating Zones in Microgravity Environment

    A.Yu. Gelfgat1, A. Rubinov2, P.Z. Bar-Yoseph2, A. Solan2

    FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 21-32, 2005, DOI:10.3970/fdmp.2005.001.021

    Abstract The three-dimensional instability of the thermocapillary convection in cylindrical undeformable floating zones heated laterally is studied numerically. Different types of the boundary conditions, including radiation heating, linearized radiation and prescribed heat flux are used in the calculation. Stability diagrams showing the Prandtl number dependence of the critical Marangoni numbers that represent the thermocapillary forcing for different heating conditions are reported. It is shown that the primary instability of initially axisymmetric thermocapillary flows is defined mainly by the total amount of heat supplied through the heated side surface. The way in which the heat is supplied More >

  • Open Access

    ARTICLE

    On the Nature and Structure of Possible Three-dimensional Steady Flows in Closed and Open Parallelepipedic and Cubical Containers under Different Heating Conditions and Driving Forces.

    Marcello Lappa1, 2

    FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 1-20, 2005, DOI:10.3970/fdmp.2005.001.001

    Abstract Possible natural transport mechanisms in cubical and shallow cavities with different heating conditions (from below or from the side) are investigated by means of numerical solution of the non-linear model equations and multiprocessor computations. Attention is focused on a variety of three-dimensional steady effects that can arise in such configurations in the case of low-Pr liquids (silicon melt) even for relatively small values of the temperature gradient due to localized boundary effects and/or true instabilities of the flow. Such aspects are still poorly known or completely ignored owing to the fact that most of the More >

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