h2. Gtheta Computations using UDF

[UDF|^UDF Gtheta.c] was created to extract the post processing result from individual cell of the model.

There are three methods in calculation the Gtheta values.

The first method is to extract the individual G and theta values from the cell and sum up all the cells to obtain the total Gtheta. The total Gtheta is then divided by the total cells to get the average Gtheta.

   ∑(G{~}cell~\*Ө{~}cell~)/N            (1)

The second method was to extract individual G value and take the average of the G value. The theta is calculated by volume divided by inlet flow rate. 
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   Ө{~}floc~ = Vol./(Vol. flow rate)
   ∑(G{~}cell~)/N\* Ө{~}floc~          (2)

The third method is multiple the sum of the G-value and the sum of the theta value and divide by the number of cells.

    ∑(G{~}cell~)/N\* ∑(Ө{~}floc~)/N             (3)
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Gtheta was also plotted using the custom function in FLUENT.
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&nbsp;&nbsp; GӨ = \[ε/υ\]^1/2^ \* \[Vol. flow rate{~}cell~/Cell Volume\]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (4)