[lucchini]

Hi Ervin,

What about the mesh?
how did you create it?
what is its size?
is the cylinder axis aligned as the z one?
are the measurements units of the mesh in meters?

Try like this: in the -180 directory of your case copy from the dieselFoam aachenBomb tutorial case the fields:
-N2
-O2
and fix as zeroGradient the boundary conditions for piston, liner and cylinderHead.

Then from the engineFoam tutorial kivaTest copy the fields:
-k
-epsilon
-T
-U
-p
and copy also the controlDict file from the /system directory in the /system directory of your case.
modify the controlDict file imposing:

adjustTimeStep yes;
maxCo 0.1;
maxDeltaT 1;

For what concerns the temperature you can, for the beginning, use the zeroGradient condition.
If the mesh is OK everything MUST work well at least till the beginning of injection.
good luck.ciao
tommaso

[adorean]

Hi Tommaso,

Thank you for your answers.

I have created the mesh with Gmsh. The cylinder axis is the z axis. The units are meters.

What about fvSchemes and fvSolution? Which ones should I use?
Now it is complaining that the Ydefault is missing from the -180 time directory.

Thanks.

Ervin

[adorean]

And after I add it, I've got a segmentation fault error.
What else is wrong?

[lucchini]

Hi all!
I was wondering if someone can give me some references about models that describe the flame kernel formation and growth in turbulent combustion and in spark-ignition engines.
thanks in advance.
ciao
tommaso

About fvSchemes and fvSolution, there's a manual for OpenFOAM in the

/OpenFOAM/OpenFOAM-1.1/doc/Guides-a4

On page 25 of Userguide.pdf there's a short description of the two files, but there's more if you read further.

/Fabian

[lucchini]

Hi!

I have a question about how StCorr is calculated. In the file StCorr.H everything is OK till Vk and Ak are calculated. It's quite difficult for me to understand how AkEst is calculated.

mgb is defined like this....

volScalarField mgb = fvc::div(nf, b, "div(phiSt,b)") - b*fvc::div(nf) + dMgb;

according to what is written after...

dimensionedScalar AkEst = gSum(mgb*mesh.V());

mgb should be the flame area per unit volume, in fact according to how the surfaceScalarField nf is defined where there is no flame (b=0 or b=1) nf is zero.

but I have some difficulties in understanding how the formula to calculate mgb is obtained.

Thanks for any kind of explanation.
regards.
tommaso

[adorean]

Hi all,

For comparison with experimental results, can the lift-off length, liquid length and flame tip penetration be computed and saved in a results file in dieselFoam?

Or, are there other variables used for validation of dieselFoam/dieselEngineFoam results?

Thanks,

Ervin

[niklas]

the dieselSpray class has a liquid length penetration function that you can use.

dieselSpray.liquidPenetration(prc)

where prc is the percentage of how much of the liquid you want to use for defining the liquid penetration.

so if you use

dieselSpray.liquidPenetration(1.0)

it will use all of the liquid to calculate the penetration, but if you use

dieselSpray.liquidPenetration(0.98)

it will not use the 2% most far away from the injector.

the other parameters, you have to calculate/define yuorself.

N

[frederic]

Hello,

I am trying kivatest with OpenFoam-1.2.

I get the following error:
FOAM FATAL ERROR : attempt to use janafThermo<equationofstate> out of temperature range

Does the bug of fixed temp always exist ?

Thanks you,

Fred

[guido_adriaensen]

Hello,

I have also tried the kivatest in OpenFOAM-1.2, again I get the error of the temperature out of range. As Henry Weller mentioned in his post of Wednesday, March 23, 2005 - 01:41 am, the problem is related to the hhu* thermodynamics packages. This would be fixed in version 1.1.1. Could It be that version 1.2 does not have this fix?? If so, is the fix available? I would really like to have it.

thanks,

Guido

[lucchini]

Hi Guido,
The 1.2 version has been fixed concerning the hhuCombustion thermo package.
You can get this error for several different reasons, and the most common is because you are using a too large time step. You can see in the kivaTest/system directory that you have two different controlDicts (controlDict.1st and controlDict.2nd), one is for compression and the other one is for combustion/expansion.
To get the case running try to reduce the time step during the combustion phase, or try to limit to (for example) 0.1 the value of the Courant Number, setting in the controlDict file the following variables:
adjustTimeStep on;
maxCo 0.1;
maxDeltaT 0.5;
I hope this should work.
Regards.
Tommaso

[guido_adriaensen]

Ciao tutti

Thx Tommaso for your reply. I have made the adjustments to the controlDict file. To be honoust, I thought I had run the kivaTest-file allready for a maximum courant number of 0.1, but after I checked it, I saw it was not configured for maximum courant number.
Sorry my mistake. :-)

Currently I'm working on a two-stroke engine, has anybody ever done a simulation for this type of engine with OpenFOAM??, if so I would gladly get into contact with that person. I'm having trouble implementing the inlet and outflow channels in the cylinderwall. They are moving with my mesh, instead of being at a fixed location. I'm currently looking at the mixer tutorial and the TJunction tutorial from Hrvoje, thx again for that! :-). When I make progress I will report this here.


regards
Guido

[guido_adriaensen]

Hello,

I still run in to the problem of the temperature range for the kivatest under version 1.2, even though I fixed the maximum courant number to 0.75. With smaller timesteps the problem is delayed, but sooner or later it kicks in. Is there something else I'm missing here? Any help will be welcome. Thx

Guido

[guido_adriaensen]

Hello Everybody,

Sorry for bothering you again, but I have a question concerning the ignition parameters defined in the ignitionSites file. The location is obvious :-), diameter is the diameter of the ignition spark, start is the starttime in degrees for ignition, duration is the time (again in degrees) for the ignition to last (in kivaTest tutorial 20 degrees, is this not too long? It seems rather long to me). If I got it wrong please let me know. The strength though is not that clear to me, what does it specify? I could not really find where it is used. If anybody could help me with this I would appreciate any hints.
Thanks all, I hope to be able to contribute some for you guys soon!

regards
Guido

[imano]

Hi, David!

I actually implemented rough wall functions, but my implementation couldn't handle non-uniform roughness and
was very ad-hoc like this:

src/turbulenceModels/incompressible/wallFunc/wallViscosityI.H:

if (yPlus > yPlusLam_)
{
if ((curPatch.name().count('~'))==2) {
nutw[facei] =
nuw[facei]
*(yPlus*kappa_.value()/(log(y_[patchi][facei]/z0_.value())) - 1.0);
} else if ((curPatch.name().count('^'))==2) {
nutw[facei] =
nuw[facei]
*(1.0/alpha_.value() - 1.0);
} else {
nutw[facei] =
nuw[facei]
*(yPlus*kappa_.value()/log(E_.value()*yPlus) - 1);
}
}

So I'm afraid my code would not help you...

Masashi

Hi,
I am trying to modelise a bluff body flamme (Sandia laboratories) using reactingFoam
After 0.041 sec, I get this message :

FOAM FATAL ERROR : attempt to use janafThermo<equationofstate> out of temperature range 200 -> 5000; T = 145

From function janafThermo<equationofstate>::checkT(const scalar T) const
in file /home/dm2/henry/OpenFOAM/OpenFOAM-1.2/src/thermophysicalModels/specie/lnInclude/ janafThermoI.H at line 73.

How can I use the functions wallAdiabatic or wallFixedTemp ? It does not work in boundary conditions.

Best regards

Julienh

Hi.

I'm starting to use OpenFOAM, and please help me.

What kind of fuels i can use in engineFoam?

Only 3 fuels(IsoOctane,Methane,Propane)??

Can I use DME...?

Please someone help me.

Atsushi

[lucchini]

Hi Atsushi,
you can use DME if you have the Gulder's coefficients for this kind of fuel (put them in combustionProperties) and also the thermophysical properties (to be set in thermophysicalProperties).
Do you want to simulate DME in a spark-ignition engine? I knew DME was used in diesel engines....
bye
Tommaso

Hi Tommaso,


I knew DME was used in diesel engine but I want to simulate in a SI engine.

Thank you for your help!!
I'll try it.

Atsushi

Hi everyone,

I try to model SI engine using engineFoam.
When I change cylinder size, read blockMesh(not to read otape17), and run engineFoam, I get this error;

FOAM FATAL ERROR : attempt to use janafThermo<equationofstate> out of temperature range 200 -> 6000; T = 0

From Function janafThermo<equationofstate>::checkT(const scalar T) const
in file: /home/dm2/henry/OpenFOAM/OpenFOAM-1.3/src/thermophysicalModels/specie/lnIncl ude/janafThermoI.H at line: 73.

FOAM aborting


Every parameter remains default except for the value of cylinder size.
I suppose that temperature T is not correctly worked.

Please someone teach me how should I do.
Any help will be welcome.
Thanks.