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The simplification of a single baffle turn eliminates eliminated important behavior within the flocculator. Multiple baffles enable separation regions to interact with each other. The velocity magnitude plot below in Figure 1 displays how the flow before separation at the second turn is not uniform and moves fastest at the edge of the baffle. The enabled us to see the interaction between different baffles.
Figure 1: Velocity Magnitude for three turns case
Figure 1 shows the flocculation tank with three baffles turning. As can be seen, the fast moving fluid after first turning propagated to the second turning.
Intuition will tell us that the velocity at the second turning will further increase because of the faster incoming flow at second bend. Surprisingly enough, at second turn, the outer edge velocity is lower compared to the first turn.
Figure 2: Turbulence Dissipate Rate for three turns
One explanation of such phenomena is that the faster moving fluid can't turn fast enough and impinges on the edge of the third baffle. The contours wall. Upon investigating contour of turbulence dissipation rate are , illustrated in Figure 2.
Figure 1: Velocity Magnitude for three turns case
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figure 2, we see that there is a very high region of energy dissipation rate right after the second turn. The high energy dissipation rate region explains why we have a smaller velocity.
Flocculation Tank with Five Baffles Turning
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This problem is rich in geometric variables, and our investigation found that a larger height baffles is more optimal. Below is the velocity and energy dissipation plots for flocculation height of .4:
Note that the overall epsilon value range (max at .01) is lower than the plot above which has a max of (.05), but has comparatively more uniform distribution for baffles turns 3 and 4.
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The plot is equivalent to 50*ε (since (2*.1)/(.1^3*4.2)=48). Similarly for the 1-turn baffle case the nondimensional parameters can be plotted:
The nondimensional values for one turn are comparable in magnitude. Similarly for the three turn case, the nondimensional epsilon values match the five turn case.
For more nondimensionalized plots of epsilon for varying geometries see...