J < 55

FIGURE 10.6 Computational grid for simulations of a disc turbine.

Rushton2urbine2 I3>lanes3>assing2hrough2 center 2)f2l 1 and3r<t2blades2

FIGURE 10.7 Predicted flow field at typical r-z planes (from Ranade et al., 2001a).

tangential velocities in the immediate vicinity and therefore lower radial velocities. In general, the overall predicted results showed satisfactory agreement with experimental data. Black box approaches used in the previous decade (Ranade and Joshi, 1990; Ranade et al, 1991) have shown that if the flow characteristics near the impeller swept surfaces are known, flow characteristics in the bulk region of the tank can be predicted with an accuracy adequate for most engineering applications. The crucial test of any a priori predictive model is therefore, whether it can predict flow near impeller blades accurately. The predicted (using a computational snapshot approach) results in the near impeller region were, therefore, examined in detail.

The predicted profiles of mean radial and tangential velocities at the impeller center plane are compared with the experimental data measured by PIV and LDA in Fig. 10.8. A similar comparison for turbulent kinetic energy is shown in Fig. 10.9.

Dimensionless radial co-ordinate, r/R

Lee and Yianneskis (1998) ■ Experimental

0 0

Post a comment