Flow-field and steady state

Figure 4.20 and  4.21 show the flow field for the different simulations when pseudo-steady state is achieved. Simulations are presented for increasing Reynolds number. Figures 4.20 and  4.21 show the velocity magnitude for a section of the reactor near to the baffles and the upflow profile calculated for sections of the cylindrical body. Flow field representations may not be compared directly for the different simulations, since velocity magnitudes are different for each simulation. However, from these pictures the intensity and the mixing capability of the discharge flow jets can be appreciated. The discharge jets generated from the impeller and responsible for the propagation of the flow to the rest of the vessel are easily observed in the bottom of the tank (red jets). Furthermore, the part of the reactor up to which the fluid motion is produced can be qualitatively estimated. Only for simulation S5 and S6 the upward flow forms a vortex extending up to the free surface. For all the other simulations, the stirring capability is reduced to $1/5$, $2/5$ and $3/5$ of the vessel volume. This is confirmed by profiles of the upward flow. Maximum value for upflow (at the base of the cylindrical body) varies in a wide range since fluid densities and angular velocities selected for the simulations are not comparable, as is the case for the laboratory reactor.

Figure 4.20: Velocity field and upflow: $Re=30$, $300$ and $Re=3000$.

Figure 4.21: Velocity field and upflow: $Re=3000$, $2 \cdot 10^5$ and $Re=3 \cdot 10^6$.