[gian93]

Hi guys.
I'm a student and i' m new in open foam simulation..
I' m trying to evaluate the flow coefficient through a poppet valve of an internal comb. engine .
I have modeled my geometry by solidworks providing a semi sphere as a rest chamber before the main inlet duct and then a another "plenum" behind the cylinder and then a another "plenum" behind the cylinder displacement (having cylindrical shape too).
the solver that i must use is rhosimpleFoam since my case is stationary , compressible.

I' ve made two type of simulation.
1) First of all i' ve tried to impose a pressure drop between inlet (semi sphere) and outlet
2) then i change the bc by imposing a mass flow rate instead of a pressure drop .

In both case i cannot reach convergence . it seems that some heavy unsteady phenomena arouse (especially around the poppet valve) that prevent the case to reach a convergent solution.

CheckMesh seems ok and not give me any warning...

I' ve try a lot of configuration : only laminar flow (instead of k-omega turbulence model) , larger cell of blockMesh ecc, larger plenum chamber at outlet .. but nothing seems work.

i' ve stayed on ths project for weeks and weeks but i didn't managed to reach any type of solution.
Could anyone help me by take a look on the case? i' ve uploaded the case via google drive at this link.




https://drive.google.com/file/d/0B_R...ew?usp=sharing







here instead i give checkMesh log:



Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 4272659
faces: 12025709
internal faces: 11751182
cells: 3903207
faces per cell: 6.09163
boundary patches: 10
point zones: 1
face zones: 3
cell zones: 0

Overall number of cells of each type:
hexahedra: 3512127
prisms: 47047
wedges: 0
pyramids: 0
tet wedges: 752
tetrahedra: 3
polyhedra: 343278
Breakdown of polyhedra by number of faces:
faces number of cells
4 51944
5 28009
6 29925
7 113169
8 53725
9 38062
10 970
11 298
12 15864
13 53
14 61
15 10827
16 6
17 1
18 363
21 1

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
inlet 56952 71836 ok (non-closed singly connected)
piatto 9949 11307 ok (non-closed singly connected)
condotto 79887 104802 ok (non-closed singly connected)
guida 4326 5685 ok (non-closed singly connected)
valvole 57033 64591 ok (non-closed singly connected)
sedi 11158 15191 ok (non-closed singly connected)
testa 26416 29430 ok (non-closed singly connected)
outlet 1581 1613 ok (non-closed singly connected)
cilindro 17224 18461 ok (non-closed singly connected)
plenum 10001 10123 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (0.0367242 -0.18 0.346475) (0.236754 0.323378 0.628011)
Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
Mesh has 3 solution (non-empty) directions (1 1 1)
Boundary openness (-3.22993e-16 -1.18435e-16 4.97165e-16) OK.
Max cell openness = 4.30493e-16 OK.
Max aspect ratio = 13.9639 OK.
Minimum face area = 2.01645e-09. Maximum face area = 6.50251e-06. Face area magnitudes OK.
Min volume = 4.14004e-13. Max volume = 1.05867e-08. Total volume = 0.00404849. Cell volumes OK.
Mesh non-orthogonality Max: 64.9158 average: 6.94015
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 3.80401 OK.
Coupled point location match (average 0) OK.

Mesh OK.

End

[gian93]

i post here some issue
i know that the case is very heavy..


control dict
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application rhoSimpleFoam;

startFrom startTime;

startTime 0;

stopAt endTime;

endTime 2500;

deltaT 1;

writeControl timeStep;

writeInterval 100;

purgeWrite 0;

writeFormat ascii;

writePrecision 6;

writeCompression off;

timeFormat general;

timePrecision 6;

graphFormat raw;

runTimeModifiable true;

functions
{

#includeFunc "residuals"
// #includeFunc "volFlowRateSurface"
// #includeFunc "pressureDifferencePatch"
//#includeFunc "staticPressure"
//#includeFunc "totalPressureCompressible"
#includeFunc "yPlus"

}


Fvschemes

FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
default steadyState;
}

gradSchemes
{
default Gauss linear;
}

divSchemes
{
default none;

div(phi,U) bounded Gauss linear;
div(((rho*nuEff)*dev2(T(grad(U))))) Gauss linear;
div(phi,e) bounded Gauss upwind;
div(phi,h) bounded Gauss upwind;
div(phi,epsilon) bounded Gauss upwind;
div(phi,omega) bounded Gauss upwind;
div(phi,k) bounded Gauss upwind;

div(phid,p) Gauss upwind;
div(phi,Ekp) bounded Gauss upwind;
div((phi|interpolate(rho)),p) Gauss upwind;
div(phi,K) bounded Gauss upwind;
}

laplacianSchemes
{
default Gauss linear corrected;
//default Gauss linear uncorrected;
}

interpolationSchemes
{
default linear;
}

snGradSchemes
{
default corrected;
}

wallDist
{
method meshWave;
}






FvSolution

FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
p
{
solver GAMG;
tolerance 1e-08;
relTol 0.1;
smoother GaussSeidel;
nPreSweeps 0;
nPostSweeps 2;
nFinestSweeps 2;
cacheAgglomeration true;
nCellsInCoarsestLevel 20;
agglomerator faceAreaPair;
mergeLevels 1;
}

U
{
solver PBiCGStab;
preconditioner DILU;

nSweeps 2;
tolerance 1e-06;
relTol 0.1;
}

"(e|h)"
{
solver PBiCGStab;
preconditioner DILU;

tolerance 1e-06;
relTol 0.1;
}

"(k|epsilon|omega)"
{
$U;
tolerance 1e-07;
relTol 0.1;
}
}

SIMPLE
{
nNonOrthogonalCorrectors 0;
rhoMin 0.1;
rhoMax 1.5;
pRefCell 0;
pRefValue 0;
residualControl
{
p 1e-4;
U 1e-4;
e 1e-4;

// possibly check turbulence fields
"(k|epsilon|omega)" 1e-3;
}
}

relaxationFactors
{
fields
{
p 0.5;
rho 0.05;
}
equations
{
U 0.7;
"(k|epsilon|omega)" 0.7;
"(e|h)" 0.5;
}
}

[gian93]

here instead the boundary conditionv(only P and U for the case with imposed pressure difference)



/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 5.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0";
object p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [1 -1 -2 0 0 0 0];

internalField uniform 101500;

boundaryField
{
inlet
{
type totalPressure;
U U;
gamma 1.4;
p0 uniform 101500;
value uniform 101500;
}
piatto
{
type zeroGradient;
}
condotto
{
type zeroGradient;
}
guida
{
type zeroGradient;
}
valvole
{
type zeroGradient;
}
sedi
{
type zeroGradient;
}
testa
{
type zeroGradient;
}
outlet
{
type uniformFixedValue;
uniformValue table
(
(0 101500)
(50 101000)
(100 100500)
(150 100000)
(200 99500)
//(50 99000)
//(60 98500)
//(70 98000)
//(80 97500)
//(90 97000)
//(100 96500)
//(110 96000)
//(120 (90000))
//(130 (85000))
//(140 (81500))
);
}
cilindro
{
type zeroGradient;
}
plenum
{
type zeroGradient;
}
}


// ************************************************** *********************** //







/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 5.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volVectorField;
location "0";
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
inlet
{
type pressureInletOutletVelocity;
value uniform (0 0 0);
U U;
}
piatto
{
type noSlip;
}
condotto
{
type noSlip;

}
guida
{
type noSlip;
}
valvole
{
type noSlip;
}
sedi
{
type noSlip;
}
testa
{
type noSlip;
}
outlet
{
type pressureNormalInletOutletVelocity;
value uniform (0 0 0);
phi phi;
}
cilindro
{
type noSlip;
}
plenum
{
type noSlip;
}
}


// ************************************************** *********************** //

[gian93]

hi!
could anyone help me?


should i use a unsteady solver?

maybe you can give me some input.
thanks.