[niklas]

Its because the chemistry mechanism is constructed at the standard temperature.

You can safely set the temperature range to 200K.

[mavimo]

Hallo Niklas,
I have set the temperature range to 200K and it work fine!

Thanks
Marco

[torvic]

Hi All,

I'm running reactingFoam in OF-1.4 64 bits and after a short time I get the following.

foam@ws-linux:~/OpenFOAM/foam-1.4/run/combustor/cpaperext/pruebas/prueba49b> #0 Foam::error::printStack(Foam:stream&)
#1 Foam::sigFpe::sigFpeHandler(int)
#2 ??
#3 Foam::sqrt(Foam::Field<double>&, Foam::UList<double> const&)
#4 Foam::tmp<foam::geometricfield<double,> > Foam::sqrt<foam::fvpatchfield,>(Foam::tmp<foam::ge ometricfield<double,> > const&)
#5 main
#6 __libc_start_main
#7 __gxx_personality_v0 at ../sysdeps/x86_64/elf/start.S:116

[1]+ Floating point exceptionreactingFoam $FOAM_RUN/combustor/cpaperext/pruebas prueba49b >reac1.log

But, if i run the same case in another machine with OF-1.4 32 bits the simulation goes on without displaying that message.

Just for clarity the 64 bit machine has SLED-10 SP1 and the 32 bit one OpenSUSE 10.2

Any comment is appreciated

thanks

V

[mattijs]

1) possibly floating point exception (sigfpe) behaviour is different on both machines. Do you have $FOAM_SIGFPE set on both machines.

2) There might be slightly different behaviour of floating point calculations, causing one architecture to have a number just within acceptable range whereas the other doesn't.

Add some printing of min and max of your field to your application and see how large it becomes.

[torvic]

Hi Mattijs

Thanks so much for the quick response. As for $FOAM_SIGFPE, it's not set.

However, the 32 bit already blowed up, but it was in the 0.088 time step, whereas with the 64 bit it was in the 0.009. Moreover, the message is slighlty different, pointing to the chemistry model. I add it just for clarity:
Solving chemistry
#0 Foam::error::printStack(Foam:stream&)
#1 Foam::sigFpe::sigFpeHandler(int)
#2 Uninterpreted: [0xb7ef2420]
#3 Foam::chemistryModel::solve(double, double)
#4 main
#5 __libc_start_main
#6 __gxx_personality_v0 at /usr/src/packages/BUILD/glibc-2.3/csu/../sysdeps/i386/elf/start.S:122
Floating point exception


I will try your suggestions of printing min/max.

thanks so much again

V

[piradeepan]

Dear All
I am working with reacting Foam solver.
Please tell me, how I can set ignition for only 1 second.
Vijay

[haghajani]

I want to model H2 dispersion through a hole in a closed box, containing O2 in it.

To do this, I disabled chemistry and turbulentReacrion (off) in chemistryProperties of reactingFoam. The problem is, the solution is very slow due to reactingFoam timing.

1- What are the equations which reactingfoam solve?
2 Is reactingfoam the proper solver? to model such a problem!

Is there any tutorial for dispersion of one Gas in to 2nd Gas?

Many thanks,
Hamed.

[haghajani]

I want to model H2 dispersion through a hole in a closed box, containing O2 in it.

To do this, I disabled chemistry and turbulentReacrion (off) in chemistryProperties of reactingFoam. The problem is, the solution is very slow due to reactingFoam timing.

1- What are the equations which reactingfoam solve?
2 Is reactingfoam the proper solver? to model such a problem!

Is there any tutorial for dispersion of one Gas in to 2nd Gas?

Many thanks,
Hamed.

[villet]

Hi Hamed,

source code for "reactingFoam" can be found at "$FOAM_APP/solvers/combustion/reactingFoam". Some files are used from "XiFoam" solver (../XiFoam directory).

You can solve your problem using "reactingFoam" in the way you explained. But if your problem is purely mixing/dispersion problem of two species, you could start wit somewhat simpler solver. I was thinking adding a passive scalar (representing H2/O2) to compressible/incompressible turbulent/laminar solver. You can find examples on this forum and OF wiki (adding temperature equation).

[haghajani]

Hi Ville,

Thanks for your kind reply,

The problem is purely Mixing/dispersion.
To do this, first I run the PitzDaily case, H2 from upper inlet and O2 from lower inlet. The mixing behaviour is acceptable. But, by changing the Geometry and the problem a bit (evacuation of H2 stream in a closed container of O2), apart from the slowness of solution (due to time-step control nature of reactingFoam), and considering effect of Gravity in "enviromentalProperties", the solution goes crazy!!! It seems mass equation does not satisfies and some mass misses and the flow field is really far from thoughts.
Anyway, I'll try on the compressible/incompressible solvers.

Reg.
Hamed

[viji]

hi
how and were to define boundary condition of separate inlets for air and fuel in a combustion problem.. i am working in XIfoam

[Javier]

Hello,

I´m working with reactingFoam case, and I would like to know how to define the start of combustion (ignition) only in a group of cells (cell zone), not in the whole system.

Also I would like to know where the autoignition temperature must be introduced.

Thank you very much in advance!

[chbenz]

Hi,

please have a look at http://openfoamwiki.net/index.php/Contrib_reactingFoam
Another way is to set T high enough to ignite your composition. You could use setField. An example is here : $FOAM_APP/utilities/setFields

Christof

[aortwein]

Originally Posted by finch

No, I did not change anything in the case, except the paths to CHEMKINFile and CHEMKINThermoFile. To make sure, I unpacked the archive again and ran the case. I got exactly the same error. Did Hannes, or anyone else, run the case all the way to completion?

It is possible to run the case. There is a minor error in the test case making trouble: in the "T"-file in the "0"-directory, the outlet is set to "type fixedValue" with a value of 800 K. By changing that to "type zeroGradient", the test case should run.

Greets, Andreas

[SilPaut]

Hi everybody!

i'm trying to simulate a dump combustor (turbulent/premixed case) with reactingFoam (OF-1.7).
The mixture is propane/air.

I have some troubles to equilibrate the the k-epsilon model. Actually it runs pretty well but I get a laminarization in correspondence of dQ "line". Which mean that mut and alphat drop down and there is not enough transport and diffusion of heat. Thus the trend of temperature along the radius (it is an axis-symmetric geometry) is very sharp comparing with the one from Fluent and experimental datas .

so I played a whit the Prt number and Cmix and i get good results with Prt=0.9 and Cmix=5.

My question is: does it make sense use a such as big value for Cmix?


so the coeffs i'm using are:

kEpsilonCoeffs
    {
        Cmu         0.09;
        C1          1.44;
        C2          1.92;
        C3          -0.33
        sigmak      1.0;
        sigmaEps    1.3;
        Prt         0.9;   
    }

and

Cmix =5

Thank you!!
Silvano

[yash.aesi]

greetings oll ,

i am using OF 2.2 and trying to solve my case with the reacting Foam solver
the doubt in my mind is that do i need to use chemkin folder along with 0, constant and system in OF 2.2 as it already have a reaction and thermo. file in constant folder as given in counterflowflame2D.



thanks in advance
Regards
sonu .