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dsmcFoam+ axissymetric simulation convergence

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Old   October 13, 2023, 04:42
Default dsmcFoam+ axissymetric simulation convergence
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Ashok Kumar
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I am running a flow through 2D axissymmetric flow through a micro-nozzle from the throat. Throat height of the nozzle is 5mm while the exit is 21mm and length of the divergent section is 50.7mm. Total number of cells in around 1,04,000, radial extent of the domain is 0.05 and maximum radial weighting factor is 50000 (I do not know how to fix this number). nEquivalentParticles of 1e8.

Though initially the simulations are running, the number of dsmc particles are going down rapidly, and large fluctuations are seen in the average kinetic energy.

I changed the radial weigting factor to 1000 and nEquivalentParticles to 0.65e10. In both the cases, particles inserted in the domain was around 30,00,000.

But in both the cases, I am having large fluctuations in average KE and dsmc particles is going to zero.

my blockmesh file:

/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 6
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 1e-3;

vertices
(
(0 0 0) //0
(5 0 0) //1
(25 0 0) //2
(50.7 0 0) //3
(100 0 0) //4
(100 20.987 0.733) //5
(100 49.969 1.744) //6
(50.7 49.969 1.744) //7
(50.7 20.987 0.733) //8
(25 11.673 0.4076) //9
(5 4.427 0.1546) //10
(0 2.498 0.0872) //11
(0 2.498 -0.0872) //12
(5 4.427 -0.1546) //13
(25 11.673 -0.4076) //14
(50.7 20.987 -0.733) //15
(50.7 49.969 -1.744) //16
(100 49.969 -1.744) //17
(100 20.987 -0.733) //18

);

blocks
(
hex (1 10 13 1 0 11 12 0) dsmcZone (120 1 240) simpleGrading (1 1 1)
hex (2 9 14 2 1 10 13 1) dsmcZone (120 1 330) simpleGrading (1 1 1)
hex (3 8 15 3 2 9 14 2) dsmcZone (120 1 120) simpleGrading (1 1 1)
hex (4 5 18 4 3 8 15 3) dsmcZone (120 1 100) simpleGrading (1 1 1)
hex (5 6 17 18 8 7 16 15) dsmcZone (100 1 100) simpleGrading (1 1 1)
);

edges
(
arc 11 12 (0 2.5 0)
arc 10 13 (5 4.43 0)
arc 9 14 (25 11.68 0)
arc 8 15 (50.7 21 0)
arc 7 16 (50.7 75 0)
arc 5 18 (200.7 21 0)
arc 6 17 (200.7 75 0)
);

boundary
(
inlet
{
type patch;
faces
(
(0 11 12 0)
);
}
outlet
{
type patch;
faces
(
(4 5 18 4)
(18 17 6 5)
(17 16 7 6)

);
}

walls
{
type wall;
faces
(
(11 10 13 12)
(10 9 14 13)
(9 8 15 14)
(8 7 16 15)
);
}
side1
{
type wedge;
faces
(
(0 1 13 12)
(1 2 14 13)
(2 3 15 14)
(3 4 18 15)
(15 18 17 16)
);
}

side2
{
type wedge;
faces
(
(0 1 10 11)
(1 2 9 10)
(2 3 8 9)
(3 4 5 8)
(8 5 6 7)
);
}

axis
{
type empty;
faces
(
(0 1 1 0)
(1 2 2 1)
(2 3 3 2)
(3 4 4 3)

);
}

);

mergePatchPairs
(

);


// ************************************************** *********************** //
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Tags
axissymmetry, dsmcfoam+, openfoam, radial weighting factor, rwf

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