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April 12, 2021, 01:51
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Mass flow rate issue
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#1 |
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New Member
parth
Join Date: Feb 2020
Posts: 23
Rep Power: 6  |
I am trying to solve flow inside an inverted L type of annulus cylinder. I am simulating for one sector of the annulus cylinder. Where there is fixed pressure is provided at the inlet. The outlet is inletOutlet boundary condition. I have set up the case according to the TJunction case, which is also pressure based flow. The inlet pressure is about ~0.21 MPa. And my working material is sodium. I have divided the inlet pressure with the sodium density, and appropriate viscosity has been provided. However, I am not getting the correct mass flow rate at the outlet compared to lumped calculations. Additionally, I took the same geometry and ran the case in fluent, I got the correct mass flow at the outlet. I am not able to figure out where I have made mistake in the OpenFOAM model.
My boundary conditions are as follows: Velocity boundary conditions Code:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: v1912 |
| \\ / A nd | Website: www.openfoam.com |
| \\/ 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);
}
walls
{
type noSlip;
}
wedge1
{
type symmetry;
}
wedge2
{
type symmetry;
}
top_walls
{
type noSlip;
}
outlet
{
type inletOutlet;
inletValue uniform (0 0 0);
value uniform (0 0 0);
}
interface3
{
type empty;
}
interface4
{
type empty;
}
}
// ************************************************************************* //
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: v1912 |
| \\ / A nd | Website: www.openfoam.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0";
object p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions [0 2 -2 0 0 0 0];
internalField uniform 0;
boundaryField
{
inlet
{
type fixedValue;
value uniform 238;
}
walls
{
type zeroGradient;
}
wedge1
{
type symmetry;
}
wedge2
{
type symmetry;
}
top_walls
{
type zeroGradient;
}
outlet
{
type fixedValue;
value uniform 0;
}
interface3
{
type empty;
}
interface4
{
type empty;
}
}
// ************************************************************************* //
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: v1912 |
| \\ / A nd | Website: www.openfoam.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0";
object k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions [0 2 -2 0 0 0 0];
internalField uniform 0.0034;
boundaryField
{
inlet
{
type turbulentIntensityKineticEnergyInlet;
intensity 0.05;
value uniform 0.0034;
}
walls
{
type kqRWallFunction;
value uniform 0.0034;
}
wedge1
{
type symmetry;
}
wedge2
{
type symmetry;
}
top_walls
{
type kqRWallFunction;
value uniform 0.0034;
}
outlet
{
type inletOutlet;
inletValue uniform 0;
value uniform 0;
}
interface3
{
type empty;
}
interface4
{
type empty;
}
}
// ************************************************************************* //
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: v1912 |
| \\ / A nd | Website: www.openfoam.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0";
object omega;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions [0 0 -1 0 0 0 0];
internalField uniform 0.1;
boundaryField
{
inlet
{
type turbulentMixingLengthFrequencyInlet;
mixingLength 1.2;
phi phi;
k k;
value uniform 0.1;
}
walls
{
type omegaWallFunction;
blended 1;
beta1 0.075;
value uniform 0.1;
}
wedge1
{
type symmetry;
}
wedge2
{
type symmetry;
}
top_walls
{
type omegaWallFunction;
blended 1;
beta1 0.075;
value uniform 0.1;
}
outlet
{
type inletOutlet;
inletValue uniform 0.1;
value uniform 0.1;
}
interface3
{
type empty;
}
interface4
{
type empty;
}
}
// ************************************************************************* //
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: v1912 |
| \\ / A nd | Website: www.openfoam.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0";
object nut;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions [0 2 -1 0 0 0 0];
internalField uniform 0;
boundaryField
{
inlet
{
type calculated;
value uniform 0;
}
walls
{
type nutkWallFunction;
value uniform 0;
}
wedge1
{
type symmetry;
}
wedge2
{
type symmetry;
}
top_walls
{
type nutkWallFunction;
value uniform 0;
}
outlet
{
type calculated;
value uniform 0;
}
interface3
{
type empty;
}
interface4
{
type empty;
}
}
// ************************************************************************* //
Code:
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object blockMeshDict;
}
scale 1;
rin 0.28;
rout 0.29;
h0 0;
h1 1.8;
delh 0.0005;
sin30 0.5;
cos30 0.8660254037844387;
cos0 1;
sin0 0;
dr1 $rout - $rin;
dr2 0.06;
// (#calc "$rin*$cos30" #calc "$rin*-$sin30" $h0) //0
// (#calc "$rout*$cos30" #calc "$rout*-$sin30" $h0) //1
// (#calc "$rout*$cos30" #calc "$rout*$sin30" $h0) //2
// (#calc "$rin*$cos30" #calc "$rin*$sin30" $h0) //3
vertices
(
(#calc "$rin*$cos30" #calc "$rin*-$sin30" $h0) //0
(#calc "$rout*$cos30" #calc "$rout*-$sin30" $h0) //1
(#calc "$rout*$cos30" #calc "$rout*$sin30" $h0) //2
(#calc "$rin*$cos30" #calc "$rin*$sin30" $h0) //3
(#calc "$rin*$cos30" #calc "$rin*-$sin30" $h1) //4
(#calc "$rout*$cos30" #calc "$rout*-$sin30" $h1) //5
(#calc "$rout*$cos30" #calc "$rout*$sin30" $h1) //6
(#calc "$rin*$cos30" #calc "$rin*$sin30" $h1) //7
(#calc "$rin*$cos30" #calc "$rin*-$sin30" $h1) //8
(#calc "$rout*$cos30" #calc "$rout*-$sin30" $h1) //9
(#calc "$rout*$cos30" #calc "$rout*$sin30" $h1) //10
(#calc "$rin*$cos30" #calc "$rin*$sin30" $h1) //11
(#calc "$rin*$cos30" #calc "$rin*-$sin30" #calc "$h1+$delh") //12
(#calc "$rout*$cos30" #calc "$rout*-$sin30" #calc "$h1+$delh") //13
(#calc "$rout*$cos30" #calc "$rout*$sin30" #calc "$h1+$delh") //14
(#calc "$rin*$cos30" #calc "$rin*$sin30" #calc "$h1+$delh") //15
(#calc "($rin+$dr1)*$cos30" #calc "($rin+$dr1)*-$sin30" $h1) //16
(#calc "($rout+$dr2)*$cos30" #calc "($rout+$dr2)*-$sin30" $h1) //17
(#calc "($rout+$dr2)*$cos30" #calc "($rout+$dr2)*$sin30" $h1) //18
(#calc "($rin+$dr1)*$cos30" #calc "($rin+$dr1)*$sin30" $h1) //19
(#calc "($rin+$dr1)*$cos30" #calc "($rin+$dr1)*-$sin30" #calc "$h1+$delh") //20
(#calc "($rout+$dr2)*$cos30" #calc "($rout+$dr2)*-$sin30" #calc "$h1+$delh") //21
(#calc "($rout+$dr2)*$cos30" #calc "($rout+$dr2)*$sin30" #calc "$h1+$delh") //22
(#calc "($rin+$dr1)*$cos30" #calc "($rin+$dr1)*$sin30" #calc "$h1+$delh") //23
);
blocks
(
// block 1 and 2, x and y direction divisions should be same
// block 2 and 3 z, y direction divisions should be same
// block 1
hex (0 1 2 3 4 5 6 7) ( 10 200 450) simpleGrading (1 1 1) // bird
// block 2
hex (8 9 10 11 12 13 14 15) ( 10 200 15) simpleGrading (1 1 1) //head
// block 3
hex (16 17 18 19 20 21 22 23) ( 40 200 15) simpleGrading (1 1 1) //beak
);
edges
(
arc 0 3 ($rin 0 $h0)
arc 1 2 ($rout 0 $h0)
arc 4 7 ($rin 0 $h1)
arc 5 6 ($rout 0 $h1)
arc 8 11 ($rin 0 #calc "$h1")
arc 9 10 ($rout 0 #calc "$h1")
arc 12 15 ($rin 0 #calc "$h1+$delh")
arc 13 14 ($rout 0 #calc "$h1+$delh")
arc 16 19 (#calc "$rin+$dr1" 0 #calc "$h1")
arc 17 18 (#calc "$rout+$dr2" 0 #calc "$h1")
arc 20 23 (#calc "$rin+$dr1" 0 #calc "$h1+$delh")
arc 21 22 (#calc "$rout+$dr2" 0 #calc "$h1+$delh")
);
boundary
(
inlet
{
type patch;
faces
(
(0 3 2 1)
);
}
walls
{
type wall;
faces
(
(7 3 0 4)
(12 15 11 8)
(2 6 5 1)
);
}
wedge1
{
type symmetry;
faces
(
(5 4 0 1)
(8 9 13 12)
(16 17 21 20)
);
}
wedge2
{
type symmetry;
faces
(
(3 7 6 2)
(15 14 10 11)
(23 22 18 19)
);
}
top_walls
{
type wall;
faces
(
(16 19 18 17)
(12 13 14 15)
(20 21 22 23)
);
}
outlet
{
type patch;
faces
(
(21 17 18 22)
);
}
// defaultFaces
// {
// type empty;
// faces
// (
// (4 5 6 7)
// (8 9 10 11)
// (23 20 16 19)
// (14 13 9 10)
// );
// }
interface1
{
type empty;
faces
((4 5 6 7));
}
interface2
{
type empty;
faces
((8 9 10 11));
}
interface3
{
type empty;
faces
((23 20 16 19));
}
interface4
{
type empty;
faces
((14 13 9 10));
}
);
mergePatchPairs
(
(interface1 interface2)
);
Thank you, Parth |
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April 12, 2021, 11:32
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#2 |
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Super Moderator
Tobias Holzmann
Join Date: Oct 2010
Location: Bad Wörishofen
Posts: 2,711
Blog Entries: 6
Rep Power: 52   |
We are not talking about a real pressure for incompressible solvers. The only thing that matters is the pressure gradient which you set with fixedValue. However, you inlet and outlet do have a fixedValue condition which tells you to have a fixed pressure gradient (static pressure).
Based on your boundary conditions, your mass-flow should increase to infinity as you don´t reduce the pressure gradient - for example - reduce the inlet pressure by the dynamic pressure. The solution of your problem should be easy:
That condition reduces the static pressure at the faces according to the dynamic pressure and keeps the total pressure equal (to the value you specified). Hence, you get an equilibrium between acceleration of your fluid and the pressure gradient. By the way. If you inlet pressure is around 0.21 MPa, you need to know which pressure you mention here. Is it the total pressure or the static pressure? You need to know the pressure at the outlet correpsonding to the same type of the inlet. Here, 0.21 MPa corresponding to your outlet is the static-pressure gradient.
__________________
Keep foaming, Tobias Holzmann |
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April 12, 2021, 12:03
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#3 |
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New Member
parth
Join Date: Feb 2020
Posts: 23
Rep Power: 6 |
Dear Tobi...!!
Thank you for your reply. I understood it should be total pressure at the inlet. I have really learnt a lot from your youtube videos, they are very much informative. Best regards, Parth |
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| Tags |
| openfoam1912, pimplefoam, pressure boundary, pressure driven flow, velocity boundary |
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