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Needing some advise about dieselEngineFoam

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Old   April 28, 2005, 05:36
Default Well, thanks Tommaso, but now
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Ervin Adorean
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Well, thanks Tommaso, but now I'm confused.

> 'maxDeltaT in an engine simulation is the MAXIMUM CRANK ANGLE (and not the TIME STEP) and it should be kept around 0.1'

What MAXIMUM CRANK ANGLE is maxDeltaT?
In dieselEngineFoam and engineFoam time=CAD, right?

Can you please explain it in more detail?

Ervin
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Old   May 2, 2005, 04:27
Default Hello, I would very much ap
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Hello,

I would very much appreciate some guidelines for using 'dieselEngineFoam'.

Is it OK to define the piston, liner and cylinderhead temp. b.c. as fixedValue?

And how is that light speed-like value of "Average Velocity for injector 0: 5.63034e+06 m/s, injection pressure = 1200 bar" calculated?
Does this need to be calculated, even if injection doesn't exist at that time?

For a calculation starting at -180 CAD and ending at -10 CAD, the injection beginning at -4.4 CAD I always get divergence sooner or later, because of a high Courant number.
Which is the best way of keeping the Courant number low?

Thanks!

Ervin
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Old   May 2, 2005, 11:27
Default Now even with a low Courant nu
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Now even with a low Courant number, I've got this error message:

Max Courant Number = 0.0900482
deltaT = 2.57864e-14

Crank angle = -178.087 CA-deg
deltaZ = 6.93889e-15
void fvMesh::makePhi() : creating zero flux field
tmp<scalarfield> polyMesh::movePoints(const pointField&) : Moving points for time -0.0197875 index 183
bool primitiveMesh::checkMeshMotion(const pointField& newPoints, const bool report) const: checking mesh motion
Min volume = 4.03647e-11. Total volume = 0.000243926. Cell volumes OK.
Min area = 3.42112e-08. Face areas OK.
Pyramid volumes OK.
Non-orthogonality check OK.
Mesh motion check OK.
void fvMesh::makeCf() : assembling face centres
void fvMesh::makeC() : assembling cell centres
void fvMesh::makeSf() : assembling face areas
void fvMesh::makeMagSf() : assembling mag face areas
clearance: 0.155971
Piston speed = 0.269091 m/s
volume continuity errors : sum local = 1.63264e-15, global = 8.5799e-19
Solving chemistry
BICCG: Solving for Ux, Initial residual = 0.604385, Final residual = 2.0787e-07, No Iterations 17
BICCG: Solving for Uy, Initial residual = 0.351684, Final residual = 7.86904e-07, No Iterations 18
BICCG: Solving for Uz, Initial residual = 0.999143, Final residual = 5.99763e-07, No Iterations 36
BICCG: Solving for h, Initial residual = 1, Final residual = 5.14966e-07, No Iterations 39


--> FOAM FATAL ERROR : attempt to use janafThermo<equationofstate> out of temperature range 200 -> 5000; T = 61502.9

Function: janafThermo<equationofstate>::checkT(const scalar T) const
in file: /home/ervin/OpenFOAM/OpenFOAM-1.1/src/thermophysicalModels/specie/lnInclude/jana fThermoI.H at line: 73.

FOAM aborting

Anybody has a hint? What is wrong in my case setup?
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Old   July 10, 2007, 00:41
Default Hello, I'm new to C++. In
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atsushi
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Hello,

I'm new to C++.
In dieselEngineFoam,
What is the relationship between "adjustTimeStep" and "maxDeltaT"?

Please teach me.
thank you.

Atsushi
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Old   July 10, 2007, 01:31
Default Hi, These parameters are in
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Masato Otsuki
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Hi,

These parameters are input at:

$FOAM_SRC/src/finiteVolume/lnInclude/readTimeControls.H

And used at:

$FOAM_SRC/finiteVolume/lnInclude/setDeltaT.H

Masato
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Old   July 10, 2007, 01:34
Default sorry, $FOAM_SRC/src/finite
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Masato Otsuki
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sorry,

$FOAM_SRC/src/finiteVolume/lnInclude/readTimeControls.H

-->

$FOAM_SRC/finiteVolume/lnInclude/readTimeControls.H

Masato
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Old   July 10, 2007, 02:16
Default Thanks, Masato. Atsushi
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atsushi
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Thanks, Masato.


Atsushi
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Old   September 14, 2007, 01:30
Default Hi, What is the unit of "dQ
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atsushi
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Hi,

What is the unit of "dQ"?
[J/&theta;]? [J/s}?

I want to calculate ROHR per clank angle.

thanks.

Atsu
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Old   September 14, 2007, 03:56
Default hi, look in the createfield
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Stephan Gerber
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hi,

look in the createfields.h-file- this file creates dQ with unit dimensionSet(1,-3,-1,0,0,0,0).
regards
stephan
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Old   October 8, 2007, 02:18
Default hi, Stephan I checked dQ di
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atsushi
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hi, Stephan

I checked dQ dimensionSet(1,-3,-1,0,0,0,0)in the createfields.h-file-.

It's not heat release rate.
dQ unit is "density per second"...??

If the unit is so,
dQ has no relation to heat release rate.
I misunderstand that "dQ = heat release rate".
Am I right?

Thanks,

Atsu
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Old   October 8, 2007, 02:26
Default check hEqn.H, the term is a
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Niklas Nordin
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check hEqn.H,

the term is a bit misleading since its divided by cp.
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Old   October 9, 2007, 21:27
Default hi,Niklas I checked hEqn.H.
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atsushi
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hi,Niklas

I checked hEqn.H.
It seems that "[dQ]=[h][RR]/[Cp]"

If,
[h]=J/kg
[RR]=kg/m3/s
[Cp]=J/kg/K

then, the unit of dQ is shown by
[dQ]= kg.K/m3/s =[1 -3 -1 1 0 0 0]

...What is this unit??

I'm new to C++,and my explanation may wrong.
Please teach me the meaning of dQ unit.

Thanks,

Atsu
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Old   November 19, 2007, 09:07
Default Hi, I was solving a case usin
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N S Prasad
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Hi,
I was solving a case using engine foam. the case solved till CA -27.6 Degs and then gave the following error.

Courant Number mean: 0.00327122 max: 0.200576
deltaT = 5.94218e-06
Crank angle = -27.6924 CA-deg
deltaZ = 6.52008e-05
clearance: 0.0190537
Piston speed = 10.9725 m/s
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
#0 Foam::error::printStack(Foam:stream&)
#1 Foam::sigFpe::sigFpeHandler(int)
#2 Uninterpreted: [0xfb1420]
#3 void Foam::fvc::surfaceIntegrate<foam::vector<double> >(Foam::Field<foam::vector<double> >&, Foam::GeometricField<foam::vector<double>, Foam::fvPatchField, Foam::surfaceMesh> const&)
#4 Foam::tmp<foam::geometricfield<foam::vector<double >, Foam::fvPatchField, Foam::volMesh> > Foam::fvc::surfaceIntegrate<foam::vector<double> >(Foam::GeometricField<foam::vector<double>, Foam::fvPatchField, Foam::surfaceMesh> const&)
#5 Foam::tmp<foam::geometricfield<foam::vector<double >, Foam::fvPatchField, Foam::volMesh> > Foam::fvc::surfaceIntegrate<foam::vector<double> >(Foam::tmp<foam::geometricfield<foam::vector<doub le>, Foam::fvPatchField, Foam::surfaceMesh> > const&)
#6 Foam::fv::gaussDivScheme<foam::tensor<double> >::fvcDiv(Foam::GeometricField<foam::tensor<double >, Foam::fvPatchField, Foam::volMesh> const&)
#7 Foam::tmp<foam::geometricfield<foam::innerproduct< foam::vector<double>, Foam::Tensor<double> >::type, Foam::fvPatchField, Foam::volMesh> > Foam::fvc::div<foam::tensor<double> >(Foam::GeometricField<foam::tensor<double>, Foam::fvPatchField, Foam::volMesh> const&, Foam::word const&)
#8 Foam::tmp<foam::geometricfield<foam::innerproduct< foam::vector<double>, Foam::Tensor<double> >::type, Foam::fvPatchField, Foam::volMesh> > Foam::fvc::div<foam::tensor<double> >(Foam::GeometricField<foam::tensor<double>, Foam::fvPatchField, Foam::volMesh> const&)
#9 Foam::tmp<foam::geometricfield<foam::innerproduct< foam::vector<double>, Foam::Tensor<double> >::type, Foam::fvPatchField, Foam::volMesh> > Foam::fvc::div<foam::tensor<double> >(Foam::tmp<foam::geometricfield<foam::tensor<doub le>, Foam::fvPatchField, Foam::volMesh> > const&)
#10 Foam::compressible::turbulenceModels::kEpsilon::di vRhoR(Foam::GeometricField<foa m::vector<double>, Foam::fvPatchField, Foam::volMesh>&) const
#11 main
#12 __libc_start_main
#13 __gxx_personality_v0 at ../sysdeps/i386/elf/start.S:122
Floating point exception


Can any one point out how i can resolve the same?

Regards,
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Old   November 20, 2007, 00:27
Default Ok. I was using a hybrid mesh
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Ok. I was using a hybrid mesh tet + hex. i put in a little more effort and changed the entire mesh to hex. and the problem has been solved. i would like to put the sim video here. but dont have a clue as to how ..

(yes u can use tet mesh for engine mesh:-)

urs,
prasad.
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