Flow-field and steady state

Figures 4.34 and  4.35 show the flow field for the different simulations when pseudo steady state is achieved. Simulations are presented for increasing Reynolds number. The same range of values is used for all the simulations to make comparison of results easier. For each simulation, the distribution of $v_r$ and $v_z$ components of velocity is shown by vectors and distribution of component $v_{\theta}$ is shown by contours. The vertical section selected for representation is the nearest to both baffles. The upflow profile calculated for the cylindrical body is also presented. Figure 4.34 shows results obtained for the range of low Reynolds numbers. It can be observed that in these conditions the stirring ability of the turbofoil turbine is confined to the lower part of of the vessel. Discharge jets from the turbofoil increase their intensity from simulation S1 to S2, but they are too weak to produce circulation upward, as shown by upflow profiles. No flow in the vertical direction is produced over $z=1.5~m$ from the bottom of the vessel. Angular motion for low Reynolds is also limited to a confined region near the turbine. There, sensible fluid rotation is transferred from the turbofoil, with a rotating region that expands far from the turbine as the Reynolds number increases. Figure 4.35 shows results obtained for the range of high Reynolds numbers. It can be observed that in these conditions the stirring ability of the turbofoil turbine is improved and affects wider regions of the vessel. Discharge jets from the turbofoil are sufficiently strong to impinge against the vessel wall, deflect upward and transport high velocity jets up to $z=2~m$ from the bottom of the vessel. The circulation produced can be evaluated by the upflow profiles that show values around $400~kg/s$ for $z=2~m$ from the bottom. Angular motion for high Reynolds is rather different from the low Reynolds simulations. Peak value of angular velocity can not be identified in the contour plots for simulation S3 and S4. In these cases, rotation of the fluid is reduced also near the turbofoil, since the radial and vertical components of the flow prevails. From contours it can be observed that rotation is not extended up to the free surface for $Re=12000$ while this is the case for the higher Reynolds number.