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Question about temperature inconsistencies for cold flow in ReactingFoam

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 :)

Hello,

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

Thanks!

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

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

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...

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)

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

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.

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

Hem, I agree with Daniel. The problem arises due to the constant increasement of pressure. In this case, the term involved with dpdt is dominant in energy equation, which causes the local temperature's divergence. However, in regular combustion model, the pressure is assumed to be constant. So there must be something wrong in the pEqn in reactingFoam. According to Daniel's advice, writing "dpdt no" in thermoPhysicalProperties file is a wise choice in the incompressible case.