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-   -   Struggling to converge! (http://www.cfd-online.com/Forums/fluent/38990-struggling-converge.html)

John December 20, 2005 03:59

Struggling to converge!
 
Hello.

I have a model of a large reservoir (approx 3000 ft (900m) x 1000 ft (300m)). I am modelling flow of water through it using standard k-epsilon turbulence model. k, epsilon and velocities are converging OK. Continuity residual is stuck at 1.00. I have played around with the URFs, but no success. Anyone got any suggestions?

John.

HS December 20, 2005 08:30

Re: Struggling to converge!
 
I suppose that you are using the segregated solver?

This means that your continuity residual in fact is not changing at all during the iterations. You could check contours of Residuals->Mass imbalance for example to see if it is that some special part of your system has got problems (could be the mesh somewhere for example).

Also, I think you should check the unscaled value of the continuity residual and compare that to the mass flow at the inlet, as recommended in the FLUENT manual. Is the mass imbalance big enough to make any difference?

Are your species residual (h2o) converging OK too?

Good luck!

/Henrik

Razvan December 21, 2005 03:29

Re: Struggling to converge!
 
If there is no inlet or outlet for your reservoir then you have no problem at all! There is nothing to converge about the continuity equation! Global residual will allways sum up to 1 if there is no fluid entering or leaving the domain.

Razvan


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