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Question about temperature inconsistencies for cold flow in ReactingFoam

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Old   July 2, 2014, 23:33
Default Question about temperature inconsistencies for cold flow in ReactingFoam
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Daniel
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Dear all,

I am new to OpenFoam so would really need your help on this.

I am simulating a cold flow in ReactingFoam by turning off chemistry and reactions. The domain consists of a single axi-symmetric jet of methane-air mixture kept at 300 K and effusing into atmospheric conditions.

When I run my simulation, after couple of time steps my temperature starts to drop and reaches less than 200 K. I get the following error message in my log file.

Courant Number mean: 0.0269748 max: 0.802111
deltaT = 2.35691e-06
Time = 0.0104522

diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for O2, Initial residual = 3.62078e-06, Final residual = 7.71731e-09, No Iterations 1
DILUPBiCG: Solving for H2O, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for CH4, Initial residual = 3.62109e-06, Final residual = 7.40187e-09, No Iterations 1
DILUPBiCG: Solving for CO2, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for h, Initial residual = 0.00432636, Final residual = 1.77774e-09, No Iterations 2
--> FOAM Warning :
From function janafThermo<EquationOfState>::limit(const scalar T) const
in file /home/hlalit/apps/OpenFOAM/OpenFOAM-2.2.0/src/thermophysicalModels/specie/lnInclude/janafThermoI.H at line 108
attempt to use janafThermo<EquationOfState> out of temperature range 200 -> 5000; T = 198.002
--> FOAM Warning :
From function janafThermo<EquationOfState>::limit(const scalar T) const
in file /home/hlalit/apps/OpenFOAM/OpenFOAM-2.2.0/src/thermophysicalModels/specie/lnInclude/janafThermoI.H at line 108
attempt to use janafThermo<EquationOfState> out of temperature range 200 -> 5000; T = 198.002
--> FOAM Warning :
From function janafThermo<EquationOfState>::limit(const scalar T) const
in file /home/hlalit/apps/OpenFOAM/OpenFOAM-2.2.0/src/thermophysicalModels/specie/lnInclude/janafThermoI.H at line 108
attempt to use janafThermo<EquationOfState> out of temperature range 200 -> 5000; T = 198.002
min/max(T) = 200, 319.785

I would really like to know why this is happening and what is it that I am doing wrong here. I have also attached my case files in this message. I would be really glad if anyone could help. Thanks so much
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File Type: zip constant.zip (10.1 KB, 8 views)
File Type: zip system.zip (3.6 KB, 7 views)
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Old   July 3, 2014, 10:11
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Hello,

Does anyone have any idea to my query above? Would really need some help.

Thanks!
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Old   July 23, 2014, 20:04
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hi, Daniel,

I've no idea if you have solved this problem.

I had an exactly same warning when I'm using LTSReactingFoam. I noticed an explanation here. It sounds reasonable, but I've tried all type of BC for my P file and there is nothing improved.

I'm wondering if you have any significant progress in this regard.

Thank you
Zhixuan
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Old   July 24, 2014, 18:18
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Try deleting the kinetic energy from the energy equation and also deleting the dpdt term by setting "dpdt no" in your thermophysical properties file.

I hope that helps
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Old   July 25, 2014, 15:30
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Daniel,

Thank you for the kindly reply.

I wanted to double check,

1) where should I delete the kinetic energy terms? Do you mean I need to make some change in the source code (EEqn.H) and recompile the LTSReactingFoam.C? So which term are you suggesting to delete?
HTML Code:
fvScalarMatrix EEqn
    (
        fvm::ddt(rho, he) + fvm::div(phi, he)
      + fvc::ddt(rho, K) + fvc::div(phi, K)
      + (
            he.name() == "e"
          ? fvc::div
            (
                fvc::absolute(phi/fvc::interpolate(rho), U),
                p,
                "div(phiv,p)"
            )
          : -dpdt
        )
      - fvm::laplacian(turbulence->alphaEff(), he)
     ==
        radiation->Sh(thermo)
      + fvOptions(rho, he)
    );

2) Do I need to add "dpdt off;" or "dpdt no;" into the thermophysicalProperty file?

I have no idea how to deal with 1), but I tried both options in 2). There is no improvement at all...
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Old   July 26, 2014, 17:56
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Hi Zhixuan,

I am no expert in OpenFoam but what I did was to comment out the 'K' terms from the energy and momentum equations, so basically recompile your code and also I crosssed out the dpdt terms from the energy equations ('dpdt no' should work)
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Old   July 26, 2014, 19:28
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Hi, Daniel,

Thank you for the reply. I'm curious about why do you have to cancel the kinetic terms. Is there any specific reason?

I found the K terms in EEqn but there is nothing related in UEqn.H. So I'm wondering which one did you mean "momentum equation" ?

By the way, I'm using the OF2.3.0.

Thank you
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Old   July 27, 2014, 21:40
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Hi Zhixuan,

I was using reactingFoam for a jet flame simulation. In reacting flows usually the enthalpy equation does not include the kinetic energy terms. I deleted the 'K' terms from the EEqn.H and the UEqn.H. Maybe in your solver they are only in the EEqn.H file.

I think it would be better to ask someone else for a specific question regarding your work.
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Old   July 28, 2014, 19:12
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Thank you Daniel,

Actually, I'm also simulating a jet type of flame. I tried deleting the kinetic energy terms but it did help. I still think it might due to the boundary conditions, and need to continue research in this regards.

Anyway, I appreciate your replies.
Zhixuan
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Old   August 8, 2014, 05:07
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any update!
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