Fluid flow from a low to a higher density liquid
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INTRODUCTION
IN a previous investigation ~the penetration of liquid into a dendritic array under forced convection was examined in aluminum alloys and a water model system. The flow penetration was found to depend primarily on the initial flow velocity and the density difference between the interdendritic and bulk liquid. However, the individual effect of these variables on flow was not clearly established. In addition, the observed flow velocities differed significantly from calculated values derived theoretically. The present investigation was undertaken to establish the effect of the initial flow velocity and density changes in the liquid on vertical fluid flow in a water model system, without dendrite barriers being present. II.
PROCEDURE
Following the previous investigation a vertical vycor tube of 50 mm inside diameter was filled with brine to a height of 155 ram. A stainless steel disc 40 mm in diameter and 2 mm thick was positioned horizontally 5 mm below the top surface of the liquid and rotated at a measured angular velocity. The vertical flow velocity in brine of uniform density was determined by measuring the position of a nylon sphere as a function of time as it moved down the tube. The nylon sphere had a density of 1.150 x 103 kg m -3 which was slightly lower than the density of the brine used in the test. Measurements were made for disc velocities between 60 and 340 r per minute. The effect of density differences in the liquid on vertical flow was determined by filling the top 55 mm of the tube with brine of density p 1 and the lower 100 mm with colored brine of higher density 02, ensuring the two solutions did not mix. Following the start of rotation of the disc, the downward movement of the interface between the two solutions was measured as a function of time. Brine solutions having densities between 1.045 and 1.087 x 103 kg m 3 were used with disc speeds between 60 to 340 r per minute. For the case of AO = 0 the interface height was measured by following the downward movement of a group of spheres of slightly lower density than the liquid.
F. WEINBERG is Professor and Head, Department of Metallurgical Engineering, The University of British Columbia, 309-6350 Stores Road, Vancouver, British Columbia V6T 1W5, Canada. Manuscript submitted January 23, 1984.
METALLURGICAL TRANSACTIONS B
OBSERVATIONS
The rotation of the horizontal disc at the top of the liquid column results in downward flow of liquid near the tube wall and upward flow along the tube axis.' The downward and upward flow velocities were observed to be relatively constant along the tube and similar in magnitude. The flow velocities measured as a function of the speed of rotation of the disc are shown by the points in Figure 1. The calculated velocities, based on solutions of the Navier-Stokes equations,~ are shown by the solid line. There is good agreement in this case between the observed and calculated velocities. The flow penetration from low to higher density liquid for a series of values of Ap and rotational speeds b
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