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.