Papers by Keyword: Gravity Effect

Abstract: Rayleigh-Taylor model, an important theory dealing with ferro-hydrodynamic ( FHD ) instability, is utilized to predict the ferro-surface tension in this study. Before hexagonal peaking patterns induced by critical magnetization of ferro-solution, the simplification from proposed theory could be further made under the consideration of normal field imposed, i.e., linear relation of free surface tension proportional to apparent ferro-weight might be successfully predicted. That offers a simple semi-formula easier to study the static ferro-surface tension. To validate above results, a self-designed ring-pull device is set up as auxiliary experimental mechanism. Here relevant test of ferro-sample in various volumetric concentration as well as field intensity will be performed. Consequently, both results accessed from ferro-experiment and theoretic analysis delivers an agreement within the working magnetic intensity 0~40 mT, where a remarkable increase of surface tension coefficient occurs at higher magnetic field for ferro-solution with denser volumetric concentration considered.

Abstract: Capillary absorption is essential to mass migration in cementitious materials. Based on previous studies, capillary rise involving gravity effects is of much greater interest in porous building materials because equilibrium is attained at the wetting front when gravitational force balance the capillary force. In this paper, two different solution forms, semi-analytical and numerical, are presented to account for the gravity effect for realistical prediction of water penetration process. The former is stable against small perturbation proved by Stepanyants [1]. The comparison of predicted results by the two methods confirms the reliability of the technique in estimating water transport.

Abstract: The effects of gravity and kinetic undercooling upon the melt/crystal interface in a vertical Bridgman-Stockbarger crystal growth system by numerical simulation. Thermal transport, melt convection and kinetic undercooling are simulated by two-dimensional transient calculations. Time evolution of the centerline interface location difference is tracked. This study then compares and discusses the results among the different gravitational acceleration. We also investigate the effects of the undercooling on the interface.

Abstract: The anisotropy of dendritic structure is characterized in this paper. The direction of move of liquid/solid interface influence the velocity of the melt flow. In the course of the experiments the liquid/solid interface was moved in three different directions: i) at right angles to the direction of gravity vector, ii) in the direction identical with it and iii) in the direction opposite to it. Our purpose was to investigate the shape of solidifying dendrites as a function of the angle included by the gravity vector and solidification [6]. The measurements were done in real images fixed by us. The following parameters were chosen for characterizeing the anisotropy of dendrites: intersection number of the test lines and dendrite interface (P), orientation factor (
), dendritic surface in volume (SV). The material was solidified by using an equipment developed by the authors. The solidification rate is a constant value: 0.001 mm/s and 0.003 mm/s, the composition of material used for modelling purposes is: SCN (succinonitrile) -2.5-3 mass% of acetone. 100 images were processed in each direction. It was necessary to rotate the images in order to count the number of intersections. A program developed by the authors was used for this purpose; the number of intersections was given by the program as a function of the angle of rotation, and the perimeter and area of the dendrites.