[adrieno]

Hi all,

I'm trying to run reactingFoam without reaction to simulate a flow of CH4 into a flow of air.
In order to do that, I adapt my case from the example counterFlowFlame2D (Turning off combustion and chemistry).

In fact, Until I refine my mesh, all was ok, the calculation was running. But now, with a "better mesh", my simulation crash while, all is fine for many iterations... In fact my max temperature is exploding suddenly... I can't understand why.

Here is my log plot and my checkMesh log, if it tells you something, let me know.

/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.2                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.2.2-9240f8b967db
Exec   : checkMesh
Date   : Apr 20 2016
Time   : 13:25:33
Host   : "SAFSV4199"
PID    : 2012
Case   : /home/saf128648/OpenFOAM/saf128648-2.1.1/2016_04/19_04_Storage_36
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Disallowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
    points:           472445
    faces:            1359732
    internal faces:   1303308
    cells:            443840
    faces per cell:   6
    boundary patches: 5
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     443840
    prisms:        0
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:     0

Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
    Upper triangular ordering OK.
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
    Patch               Faces    Points   Surface topology                  
    SymmetryPlan        47424    47885    ok (non-closed singly connected)  
    outlet              1460     1549     ok (non-closed singly connected)  
    inletAir            227      283      ok (non-closed singly connected)  
    wall                7307     7760     ok (non-closed singly connected)  
    inletGas            6        14       ok (non-closed singly connected)  

Checking geometry...
    Overall domain bounding box (0 0 0) (4.5 4.5 14.76)
    Mesh (non-empty, non-wedge) directions (1 1 1)
    Mesh (non-empty) directions (1 1 1)
    Boundary openness (1.74398e-16 -2.25257e-15 -5.84921e-17) OK.
    Max cell openness = 6.43717e-16 OK.
    Max aspect ratio = 125.438 OK.
    Minimum face area = 6.63975e-05. Maximum face area = 0.0491183.  Face area magnitudes OK.
    Min volume = 2.23111e-05. Max volume = 0.00156784.  Total volume = 136.375.  Cell volumes OK.
    Mesh non-orthogonality Max: 50.7271 average: 14.0983
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 2.49936 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

End

[muhsinkhan]

what deltaT are your running with(considering that you are working with tranisant reactingFoam) and your courant number based on your new mesh ?? What was your aspect ratio and non-orthorgonality in the previous mesh ??

[adrieno]

Hi,
I've been able to run my case by refining more properly my mesh.
Now here is my checkMesh result :

Checking geometry...
    Overall domain bounding box (-4.5 -4.5 0) (4.5 4.5 14.76)
    Mesh (non-empty, non-wedge) directions (1 1 1)
    Mesh (non-empty) directions (1 1 1)
    Boundary openness (-1.517e-16 1.81499e-17 6.96523e-15) OK.
    Max cell openness = 3.19604e-16 OK.
    Max aspect ratio = 43.1992 OK.
    Minimum face area = 0.000100039. Maximum face area = 0.0425044.  Face area magnitudes OK.
    Min volume = 8.01645e-06. Max volume = 0.00111563.  Total volume = 551.126.  Cell volumes OK.
    Mesh non-orthogonality Max: 51.4972 average: 13.2434
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 1.43861 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

what do you think of that ?

I'm now trying to run my case with multi core.

Something is wondering when I plot the residuals...
In fact two things are wondering me :

First:
Concerning the inertSpecie in the file thermophysicalProperties.
As I couldn't see the residual of N2, I change it and I put CO2 instead.
What does it change concretely ? (In my case there's no reaction, I turned off chemistry and combustion)

Second:
I have exactly the same residuals for my three species in my case (N2, O2 and CH4)... How could it be ? Shouldn't they have each their own residuals ???

Thank you,
Adrien

[muhsinkhan]

Hi Adrien

your mesh seems fine

You can't see N2 as it is not calculated in any iteration, it is treated a inert. You changed it with CO2 which means you defined CO2 dictionary in your 0 folder?

Turning off the chemistry and combustion could be one of the reason why the residuals of all the species is the same. I ran your conditions on the tutorial and got exactly what you have said .. residuals are the same.

[adrieno]

Hi muhsinkhan, thank you very much for your time !!

I actually haven't any CO2 file in my 0 folder because I don't need it (I'm running my case without combustion and chemistry). But I still have a CH4 file in my 0 folder otherwise the solver doesn't run.... That should be a placeholder I think in my case. (By the way if you have any information on that, I would be glad of hearing it !)

As I said, I am questioning myself about the utility of the definition of "inertspecie". Is it a placeholder when using reactingFoam with chemistry and combustion turned off ?

I still can't understand why there's no difference on my residuals of my three species (O2, N2, CH4)... Because for sure, the speed (as the energy, the pressure ...) is completely different for the 3 species...

What do represent exactly residuals ploted by openFoam ? (I mean the residual log appearing on terminal, then plotted with gnuplot or anything else)