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May 6, 2013, 16:08 |
Problem with flow through nanonozzle
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New Member
Sam
Join Date: May 2013
Posts: 1
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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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