Radial and axial liquid velocity distributions in the tapered riser were investigated theoretically and experimentally. The liquid velocity distributions were computed by solving the NavierStokes equation numerically based on a modified mixing-length theory. Both radial and axial components of liquid velocity were taken into account. As a result, we found that the radial velocity component was much smaller than the axial velocity component. For a cylindrical column, which means no tapered section, a simplified solution was obtained. The simplified solution was found to agree well with the rigorous numerical solution even in the tapered riser. To confirm the validity of the present hydrodynamic model, the velocity distributions in the tapered riser were measured by an electric probe method using KCI solution as a tracer. The measured velocity distributions agreed with the computed ones, except in the vicinity of the bottom of the tapered riser at high gas flow rates.On a etudie de maniere theorique et experimentale les distributions de vitesse radiale et axiale du liquide dans une colonne montante conique. Les distributions de vitesse du liquide ont ete calculees par ordinateur en resolvant numeriquement I'equation de Navier-Stokes d'apres une theorie de longueur de melange modifiee. Les deux composantes radiale et axiale de la vitesse du liquide ont ete prises en consideration. C o m e consequence, nous avons trouve que la composante de vitesse radiale etait beaucoup plus petite que la composante de vitesse axiale. Pour une colonne cylindrique, c'est-a-dire sans section conique, on a obtenu une solution simplifiee. On a trouve que cette solution simplifiee concordait bien avec la solution numerique rigoureuse m&me dans la colonne montante conique. Afin de confirmer la validite du present modele hydrodynamique, les distributions de vitesse dans la colonne montante conique ont ete mesurees au moyen d'une sonde electrique et d'une solution de KCI comme traceur. Les distributions de vitesse mesurees concordent avec les distributions calculees par ordinateur, excepte dans le voisinage du fond de la colonne montante conique a de forts debits de gaz.
The aim of this paper is to investigate fundamental damage behaviour of metallic materials such as aluminum, carbon steel and titanium, which have typically different crystal structures, by the single impact from low velocity to hypervelocity. Impact tests by a WC ball were performed on the three metallic materials at various impact velocities and at normal angle. Both two-stage light gas gun and ordinary air gas gun were used in this study. Indentation shapes on a cross-sectional surface and the ratios of crater diameter and depth to the diameter of the WC ball were examined. Three modes were recognized in indentation configurations independent of the type of materials. Average contact pressure, which was obtained by the impact energy divided by indentation volume, showed not only a mechanical property of the target material during the impact process but also fracture strength of the projectile, A single particle impact test at a shallow impact angle and at a hypervelocity showed huge material removal even if its single impact and suggested the difference in mechanism of the material removal between subsonic and hypervelocity impacts.
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