Gtheta Computations using UDF
Methodology
A User Defined FLUENT script (UDF) was created to extract the G_theta value from the flocculator. The UDF loops through all of the individual cells of the converged solution, and extracts the energy dissipation^1/2 times the cell area. The sum of this quantity for all cells divided by flow and square of viscoisty results in the G_theta value of the entire flocculator as shown in equation 1.
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The Gθ_baffle values weighted by the area or number of cells were also examined, but these formulations do not produce sensible results.
Gθ Computation
Below is the G_theta value presented Gθ values for flocculation tanks of different geometries:
Case Geometry (h-height,b-width,N-baffles) | Gθ_Flocculator |
|---|---|
b=.1, h=1, N=1, Clearance height=.15 | 430 |
b=.1, h=.3, N=5, sym bc | 1330 |
b=.1, h=.2, N=5 | 1060 |
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Normalizing the Gθ parameter
The Gθ value increases with increasing flocculation tank volume. Thus, when comparing different designs, each case should be normalized by the volume (or area for 2D geometries). This results in the following normalized values.
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