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Problem with flow through nanonozzle

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Old   May 6, 2013, 16:08
Default Problem with flow through nanonozzle
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Sam
Join Date: May 2013
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Hi. I'm a new OpenFOAM user and am working on simulating high pressure flow through a nanonozzle. I built my mesh using a wedge to speed up computation time and have set my boundary conditions as best I can. I'm using sonicFoam to allow for potential supersonic flow through the nozzle. Currently, I can run blockMesh and sonicFoam without errors, but when I check the results using paraFoam or probes, there appears to be no flow through the nozzle. I'm not sure if this is a problem with my mesh or my boundary conditions, so I will post both if that helps anyone figure out what I'm doing wrong.

Here is my blockMeshDict file

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 1e-9;

vertices
(
(0 0 0) //0
(499.52 0 -21.810) //1
(499.52 250 -21.810) //2
(0 250 0) //3
(499.52 0 21.810) //4
(499.52 250 21.810) //5
(61.941 250 -2.7044) //6
(24.976 300 -1.0905) //7
(0 300 0) //8
(61.941 250 2.7044) //9
(24.976 300 1.0905) //10
(61.941 350 -2.7044) //11
(0 350 0) //12
(61.941 350 2.7044) //13
(499.52 350 -21.810) //14
(499.52 600 -21.810) //15
(0 600 0) //16
(499.52 350 21.810) //17
(499.52 600 21.810) //18
);

edges
(
arc 1 4 (499.695 0 17.45)
arc 2 5 (499.695 250 17.45)
arc 6 9 (61.962 250 2.164)
arc 7 10 (24.985 300 0.8725)
arc 11 13 (61.962 350 2.164)
arc 14 17 (499.695 350 17.45)
arc 15 18 (499.695 600 17.45)
);


blocks
(
hex (0 4 1 0 3 5 2 3) sectionA (20 1 20) simpleGrading (1 1 1)
hex (3 9 6 3 8 10 7 8) sectionB (20 1 20) simpleGrading (1 1 1)
hex (8 10 7 8 12 13 11 12) sectionC (20 1 20) simpleGrading (1 1 1)
hex (6 9 5 2 11 13 17 14) sectionD (20 1 20) simpleGrading (1 1 1)
hex (12 17 14 12 16 18 15 16) sectionE (20 1 20) simpleGrading (1 1 1)
);



boundary
(
inlet
{
type patch;
faces
(
(0 1 4 0)
);
}

outlet
{
type patch;
faces
(
(16 15 18 16)
);
}

walls1
{
type wall;
faces
(
(2 1 4 5)
(7 6 9 10)
(11 7 10 13)
(15 14 17 18)
);
}

walls2
{
type wall;
faces
(
(6 2 5 9)
(14 11 13 17)
);
}

//empty
//{
//type empty;
//faces
//(
// (7 5 15 13)
// (6 4 14 12)
// (7 6 12 13)
//);
//}

symmetry1
{
type wedge;
faces
(
//(0 2 18 16)
(0 3 2 1)
(3 8 7 6)
(8 12 11 7)
//(6 11 14 2)
(12 16 15 14)
);
}

symmetry2
{
type wedge;
faces
(
//(0 1 17 16)
(0 4 5 3)
(3 9 10 8)
(8 10 13 12)
//(9 5 17 13)
(12 17 18 16)
);
}

center
{
type patch;
faces
(
(0 3 3 0)
(3 8 8 3)
(8 12 12 8)
(12 16 16 12)
);
}

interfaces
{
type patch;
faces
(
(3 6 9 3)
(12 11 13 12)
);
}


empty
{
type empty;
faces
(
(9 5 17 13)
(6 2 14 11)
(9 6 11 13)
(5 2 14 17)
);
}
);
mergePatchPairs
(
);

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

Here is my 0/p file

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform 100;

boundaryField
{
inlet
{
type fixedValue;
value uniform 6894757;
gamma 1.66;
}

outlet
{
type waveTransmissive;
value uniform 1;
field p;
gamma 1.66;
phi phi;
rho rho;
psi psi;
}

walls1
{
type zeroGradient;
}

walls2
{
type zeroGradient;
}

symmetry1
{
type wedge;
}

symmetry2
{
type wedge;
}

empty
{
type fixedValue;
value uniform 0;
}

interfaces
{
type waveTransmissive;
value uniform 800;
field p;
gamma 1.66;
phi phi;
rho rho;
psi psi;
}

center
{
type waveTransmissive;
value uniform 800;
field p;
gamma 1.66;
phi phi;
rho rho;
psi psi;
}
}

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

and my 0/U file

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volVectorField;
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform (0 1 0);

boundaryField
{
inlet
{
type pressureInletVelocity;
value uniform (0 0 1);
}
outlet
{
type waveTransmissive;
value uniform (0 1 0);
field U;
gamma 1.66;
phi phi;
rho rho;
psi psi;
}
walls1
{
type slip;
}

walls2
{
type slip;
}

empty
{
type fixedValue;
value uniform (0 0 0);
}

symmetry1
{
type wedge;
}

symmetry2
{
type wedge;
}

center
{
type waveTransmissive;
value uniform (0 1 0);
field U;
gamma 1.66;
phi phi;
rho rho;
psi psi;
}

interfaces
{
type waveTransmissive;
value uniform (0 1 0);
field U;
gamma 1.66;
phi phi;
rho rho;
psi psi;
}
}

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


Additional information:
I'm trying to simulate helium gas going through the nozzle. I'm modeling a system which I built and experimented with, so I know that there should be flow. My nanonozzle is cooled to 77K, so I also have a 0/T file which sets my temperatures to 77K. I have a large volume of helium at high pressure in the inlet so that the pressure should be approximately constant at the inlet and the outlet connects to a mass spectrometer which applies a vacuum. Using Knudsen number calculations. I found that I am in the slip flow regime, which is why I currently have my boundary conditions at the walls set to slip flow.

Thanks in advance for any help you can provide.

Last edited by sgn11; May 6, 2013 at 19:11.
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