Figure
11. Dimensionless r -zvelocity vectors and contour plots colored by the dimensionless velocity
magnitude, U /U tip on threer -z planes. (a) P10, (b)
P45, (c) P-10.
Moreover, some stagnant zones are observed on differentr -z sampling planes. For the plane of P10,
which is just before the baffle in the rotation direction, two strip
stagnant zones occur near the wall of the vessel due to the baffle
effect. A common inverted-triangle stagnant zone appears just below the
fixed ring on three sampling planes, whereas it does not occur in the
zone up the fixed ring. This stagnant zone might be eliminated by the
configuration optimization in the future study.
To examine the distributions of the axial flow and the radial flow
generated by the MBC agitator, 3D contour plots of the dimensionless
mean axial velocities and radial velocities at different axial positions
are displayed in Figure 12. Obviously, the liquid is sucked from the
top, and then move downwards rotationally in the upper part of the tank.
Meanwhile in the lower part, the liquid is pumped from the bottom, and
then move upwards rotationally. 3D contour plots of the radial
velocities in Figure 12b show that similar distributions of the radial
velocities in a wide range of axial positions (z/H =0.25 toz/H =1.0) are obtained, which should be attributed to the radial
pumping of the long blades. These axial and radial flow characteristics
ensure the high-level TKE with narrow distribution in the tank generated
by the MBC agitator.