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-   -   Draft tube and MFR/SG (http://www.cfd-online.com/Forums/cfx/19669-draft-tube-mfr-sg.html)

nyatoto June 3, 2003 05:55

Draft tube and MFR/SG
 
Hi All,

I have modelled a stirred tank with a draft tube using MFR and SG approaches. The draft tube was located on the stationary frame and the unmatched boundary was at a radial distance of about 0.58 diameter of the tank. Now I want to reduce the diameter of the draft tube so that I can have a higher flow rate in the draft tube than that in the annulus. This means that I have two choices to make:

(1) The draft tube will be on the rotating frame or (2) The unmatched boundary will have to be moved closer to the impeller tip so that the draft tube remains on the stationary frame.

I have read somewhere that as for SG, the radial position of the unmatched boundary is not critical, but is is critical for the MFR approach (about 0.585 tank diameter).

Could some one kindly expalin to me the numerical implications of the two options.

Many thanks for your time.

Regards nyatoto



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