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EMMS drag model UDF

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Old   May 21, 2014, 11:04
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  #21
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rkhr
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Hi Ignacio,
I think, you have some problem with your code…
If you do not mind, you can send me the code and I can check it.
kah.recep@gmail.com
best regards,
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Old   May 21, 2014, 20:47
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Hi Kanarya:

I applied the modifications to the code you recommended to me, but I'm still getting the same error messages:

Updating solution at time level N... done.
iter continuity u-aire u-solidos v-aire v-solidos gt-solidos k epsilon vf-solidos time/iter
# Divergence detected in AMG solver: mp-x-momentum -> Decreasing coarsening group size!
# Divergence detected in AMG solver: mp-x-momentum -> Increasing relaxation sweeps!
# Divergence detected in AMG solver: pressure correction -> Turning off correction scaling!

Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: vof-1
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: vof-1
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: vof-1
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: vof-1# Divergence detected in AMG solver: pressure correction -> Increasing relaxation sweeps!

Primitive Error at Node 0: floating point exception

Primitive Error at Node 1: floating point exception

Primitive Error at Node 2: floating point exception

Primitive Error at Node 3: floating point exception

Error: floating point exception
Error Object: #f

I'm using a non-uniform grid in radial direction, and thinking that this could be a problem, I returned to a radial uniform grid, but I got the same error messages for the uniform grid case.

Then I changed the UDF drag model to modified Syamlal-O'Brien as wrttien in the Fluent UDF manual example and the case start and continue running properly without any error messages, so I'm sure the problem is the EMMS UDF drag model.

Any help is very welcome

Regards,

Ignacio
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Old   May 24, 2014, 13:01
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Dear all, finally I found what is the problem. According many papers the initial conditions for riser simulations are setting as Vg=0.0, Vs=0.0, so when the run starts, the Reynold number becomes 0.0, and Cd becomes no-definded, and then the run crashes.

In fact my EMMS UDF drag function commented by Kanarya, including some minor modifications done by myself is working properly.

Now I defined initial Vg as 1e-6, and the case is able to start doing 2 iterations, now my problem is flow reversal detected in pressure outlet, but I think i'm walking in the right direction.

Regards,

Ignacio
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Old   June 2, 2014, 15:53
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Dear all:

Finally I found the problem, my EMMS drag model code was not correct, be careful about writing the code properly, and be careful about the if's and else if's statements.

Thanks again Kanarya.

Good luck doing CFD simulations.

Regards,

Ignacio
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Old   July 18, 2014, 06:21
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Rajani Kant Baro
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Can You tell me how to solve the non-linear equations in variables a & Usc?
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Old   January 7, 2015, 06:32
Default EMMS DRAG MODEL for gas solid flow
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sourav ganguli
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Can anyone tell me the operating condition to run emms drag model?
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