FIGURE 10.21 Schematic of stable flow patterns observed with dual Rushton turbines (from Rutherford et al., 1996). (a) Parallel flow, (b) merging flow, (c) diverging flow.

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FIGURE 10.22 Comparison of experimental ((a) Rutherford et al., 1996) and predicted ((b) Deshpande and Ranade, 2001) results for dual Rushton turbines (Parallel flow regime).

separation, predicted results clearly show the merging of impeller streams at an elevation midway between the two impellers, as was observed in the experiments. The influence of lower impeller clearance from the vessel bottom on the direction of the impeller stream was also predicted quite well, leading to the diverging flow pattern. Similar interaction between impeller streams was also evident from the contours of the predicted turbulence kinetic energy (not shown here). Qualitatively, these results agree fairly well with the experimental results reported by Rutherford et al. (1996). However, the predicted values of turbulent kinetic energy are slightly lower than the experimental data. Quantitative comparison of predicted mean velocity and experimental data is shown in Figs 10.25 and 10.26 for two different values of radial positions. These results indicate that the computational snapshot approach could adequately simulate the three different flow patterns having varying degrees of interaction

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