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-   -   Converge (http://www.cfd-online.com/Forums/fluent/119095-converge.html)

tangfl June 9, 2013 23:25

Converge
 
hi,
I'm study on external flow in sand domain, does i always need to wait the solution until converge. As it take longer time to converge for external flow and in transient state..

sina.sh June 10, 2013 00:33

Quote:

Originally Posted by tangfl (Post 432996)
hi,
I'm study on external flow in sand domain, does i always need to wait the solution until converge. As it take longer time to converge for external flow and in transient state..

Dear tang
if you want final solution, you must use steady-state solver not transient.

Regards

tangfl June 10, 2013 00:40

when i use steady state, error will be detected:

divergence detected in AMG solver: k increasing relation sweep

Why this error will appear??

sina.sh June 10, 2013 00:54

If all settings are ok, usually this error appears when initial conditions for k and epsilon are incorrect. Plz change initial conditions for k & epsilon.

tangfl June 10, 2013 02:11

i'm setting :
Inlet. Turbulent intensity = 5%. Turbulent viscosity ratio= 10
Outlet turbulent intensity=1% turbulent viscosity ratio= 10

Any problem in my setting ?

sina.sh June 10, 2013 02:21

Quote:

Originally Posted by tangfl (Post 433008)
i'm setting :
Inlet. Turbulent intensity = 5%. Turbulent viscosity ratio= 10
Outlet turbulent intensity=1% turbulent viscosity ratio= 10

Any problem in my setting ?

its your boundary condition and seems ok! you should change INITIAL CONDITION. By default initial condition for k and epsilon is 1 in fluent. Plz see
http://www.cfd-online.com/Forums/ope...urbulence.html

Regards

tangfl June 10, 2013 06:47

So, I should lower my k and epsilon value. Does I need to change relaxation values?

Why should I change my k and epsilon value? Actually what value is the most possible for k and epsilon

sina.sh June 10, 2013 07:27

Yes. you should select lower value for k and epsilon. initial value of k and epsilon are depended to your problem. but initial values havent any effect on final solution. so change value of k and epsilon to 0.001 and 0.0001 respectly.

Regards

tangfl June 10, 2013 23:00

I'm trying to lower my k and epsilon in my solution control, however the error (divergent detected) become more faster (in lesser iteration calculation).

sina.sh June 10, 2013 23:29

Is your mesh dimension correct?

tangfl June 11, 2013 02:06

how to check whether why mesh is correct?? There is no warning on my mesh,,, Do u mind send me your email...i will send my case data for u, to better understanding on my fluent setting.

sina.sh June 11, 2013 02:27

I send my mail for you (private message). please send your geometry dimension too.

tnx

tangfl June 26, 2013 03:22

i already send to u past two week..

shmilyhan September 21, 2013 21:53

help
 
Quote:

Originally Posted by tangfl (Post 432996)
hi,
I'm study on external flow in sand domain, does i always need to wait the solution until converge. As it take longer time to converge for external flow and in transient state..

do you have converge sofeware ?Can you give me a Decoding software?


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