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T-Junction using rhoPimpleFoam (Simulation blows and weird result)

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Old   July 22, 2015, 23:29
Default T-Junction using rhoPimpleFoam (Simulation blows and weird result)
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KGN
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Hi All,

I am trying to simulation T-Junction using rhoPimpleFoam (One Inlet, two Outlet). Mass Flow BC at both inlets (thats my requirement).

Simulation blows after some time and the results looks weird. Velocity goes to 2750 m/s. What might the problem.

I have attached the BC and problem setup, also vector plot.

Error Msg

-> FOAM FATAL ERROR:
Maximum number of iterations exceeded

From function thermo<Thermo, Type>::T(scalar f, scalar T0, scalar (thermo<Thermo, Type>::*F)(const scalar) const, scalar (thermo<Thermo, Type>::*dFdT)(const scalar) const, scalar (thermo<Thermo, Type>::*limit)(const scalar) const) const
in file /home/umagopinath/OpenFOAM/OpenFOAM-2.3.0/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 76.

FOAM aborting


Thanks
KGN
Attached Images
File Type: jpg Vector_Plot.jpg (34.2 KB, 6 views)
Attached Files
File Type: zip rho_test.zip (5.6 KB, 2 views)
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Old   July 23, 2015, 01:15
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KGN
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I simulated the same case using "rhoCentralFoam" and the results converges. Attached Vector plot.

But for the same Co number the time step is significantly less in "rhoCentralFoam".

Co number 0.55

rhoCentralFoam = 3.2e-7
rhoPimpleFoam = 2.2e-06

Why such a difference?
But with rhoPimpleFoam the simulation blows after some time and also the results are weird.


I guess the boundary condition is creating the problem with "rhoPimpleFoam" solver. I know only mass inflow and mass outflow of the system plus total temperature at inlet.

Thanks
KGN
Attached Images
File Type: jpg vector_plot_rhoCentralFoam_Solver.jpg (33.3 KB, 4 views)

Last edited by mecbe2002; July 23, 2015 at 03:06.
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Old   July 23, 2015, 05:50
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Wouter van der Meer
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hello mecbe2002,


I am not experienced with rhoPimpleFoam or rhoPisoFoam but looking at your system I think it is over dimensioned. You can only set one Inlet and one outlet mass flow so the system can calculate the second outlet mass flow based on a fixed outlet pressure.


Best regards
Wouter
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Old   July 23, 2015, 06:29
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KGN
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Hi wouter,

Thank for the reply.

Yes i too thinks so. But the problem is that, I know only mass flow rate/mass flux at inlet and mass flow rate at outlet.
For pressure based solver, one pressure and one velocity has to specified.

Is there is way to solve this problem?

Thanks
KGN
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Old   July 23, 2015, 15:26
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Wouter van der Meer
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hello mecbe2002,
The easiest way I can think of is guessing a pressure and calculating with this to steady state and checking this with what you want and try another pressure and calculating again and so iterating till you got your solution.

hope this helps
Wouter
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