[skuznet]

Dear FOAMers

I'm new in OpenFoam and would like to model steady state conjugate heat transfer(solid and fluid region) in a heat exchanger which consists of a few vertical metal plates attached to a horizontal plate with fluid flowing in gaps between plates.

My current experience with OpenFoam is restricted by “Lid-driven cavity flow tutorial” and “Stress analysis of a hole” tutorials. I know that there are “chtMultiRegionFoam” and “chtMultiRegionSimpleFoam” cases in /tutorials/heatTransfer/ folder. However, i didn't findt tutorials which would explain these cases and it's hard to understand what is going on in these cases without explanation.

I wonder if there is a step-by-step tutorial similar to “Lid-driven cavity” tutorial explaining conjugate heat transfer.
I also wonder if there are tutorials explaining
- how to create a case containing regions with different properties(fluid and solid), assign regions and boundaries;
- how to use conjugate heat transfer solvers;

My next step will be to model a steady state conjugate heat transfer in a porous material consisting of orthogonally interlaced cylindrical wires and fluid between them. I have a geometry for this case created in Abaqus.

I wonder if there is any way to translate my geometry from Abaqus to Open Foam preserving surfaces and regions definitions. Or what would be appropriate tool consistent with Open FOAM where I can create such geometry and define regions and surfaces?

Thank you!

[wyldckat]

Greetings skuznet and welcome to the forum!

Have a look into this (unofficial) tutorial: http://openfoamwiki.net/index.php/Ge..._-_planeWall2D - and feel free to add information to it, when you've understood better how things work!

As for Abaqus, I have no idea if there is a direct way. You can try looking here in the forum. You can even use Google:

site:www.cfd-online.com/Forums/ Abaqus OpenFOAM

If there is no such direct conversion, have a look into this wiki page and the links therein: http://openfoamwiki.net/index.php/SnappyHexMesh

Best regards,
Bruno

[skuznet]

Bruno,
thank you for your answer.
Actually I've run already the planeWall2D case. It didn't work. There was an error message in log.chtMultiRegionSipleFOAM

/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.2                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.2.2-9739c53ec43f
Exec   : chtMultiRegionSimpleFoam
Date   : Nov 22 2013
Time   : 19:54:37
Host   : "scyld.localdomain"
PID    : 65269
Case   : /home/skuznetsov/OpenFOAM/RUN/planeWall2D
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Disallowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time



--> FOAM FATAL IO ERROR: 
keyword regions is undefined in dictionary "/home/skuznetsov/OpenFOAM/RUN/planeWall2D/constant/regionProperties"

file: /home/skuznetsov/OpenFOAM/RUN/planeWall2D/constant/regionProperties from line 18 to line 20.

    From function dictionary::lookupEntry(const word&, bool, bool) const
    in file db/dictionary/dictionary.C at line 402.

FOAM exiting

and I also had error message when was trying to open results with paraview

ERROR: In ..\..\..\src\VTK\IO\vtkOpenFOAMReader.cxx, line 7200
vtkOpenFOAMReaderPrivate (058864C8): Error reading line 58 of E:\Dropbox\planeWall2D\constant/bottomAir/polyMesh/boundary: Expected number, string or (, found ;


ERROR: In ..\..\..\src\VTK\IO\vtkOpenFOAMReader.cxx, line 7200
vtkOpenFOAMReaderPrivate (058865E0): Error reading line 58 of E:\Dropbox\planeWall2D\constant/topAir/polyMesh/boundary: Expected number, string or (, found ;


ERROR: In ..\..\..\src\VTK\IO\vtkOpenFOAMReader.cxx, line 7200
vtkOpenFOAMReaderPrivate (058866F8): Error reading line 47 of E:\Dropbox\planeWall2D\constant/wall/polyMesh/boundary: Expected number, string or (, found ;


ERROR: In ..\..\..\src\VTK\Filtering\vtkExecutive.cxx, line 756
vtkCompositeDataPipeline (05BAEC40): Algorithm vtkPOpenFOAMReader(05AD8AA8) returned failure for request: vtkInformation (05B304F0)
  Debug: Off
  Modified Time: 95148
  Reference Count: 1
  Registered Events: (none)
  Request: REQUEST_INFORMATION
  FORWARD_DIRECTION: 0
  ALGORITHM_AFTER_FORWARD: 1

[wyldckat]

Hi Sergey,

Have a look into the wiki page again: http://openfoamwiki.net/index.php/Ge..._-_planeWall2D - I've added an adapted case for OpenFOAM 2.2.

Best regards,
Bruno

[skuznet]

Awesome! Thank you Bruno!

[skuznet]

Bruno,
the case now seems to run well.
But when I'm trying to open it paraview I still can't see anything.
I downloaded all case files on my pc and trying to open it with paraview (i tried versions 3.81, 3.12, 3.98.0).
-I choose .OpenFOAM file to open,
-choose OpenFOAM reader,
-check Mesh Regions box
-and click Apply
and nothing appears.

I see message

ERROR: In ..\..\..\src\VTK\IO\vtkOpenFOAMReader.cxx, line 4498
vtkOpenFOAMReaderPrivate (05944570): Error opening E:\Dropbox\planeWall2D\constant/polyMesh/faces.gz: Can't open. If you are trying to read a parallel decomposed case, set Case Type to Decomposed Case.

ERROR: In ..\..\..\src\VTK\Filtering\vtkExecutive.cxx, line 756
vtkCompositeDataPipeline (05CB2EA0): Algorithm vtkPOpenFOAMReader(05B9E960) returned failure for request: vtkInformation (05BE93C8)
  Debug: Off
  Modified Time: 98373
  Reference Count: 1
  Registered Events: (none)
  Request: REQUEST_DATA
  FROM_OUTPUT_PORT: 0
  FORWARD_DIRECTION: 0
  ALGORITHM_AFTER_FORWARD: 1

I can get rid off this message by choosing Case Type: Decomposed Case
but still don't see anything.

The time panel is not active, I can't change time and in Color panel I can't choose anything except Solid Color.

If I open the cavity case, then I can see geometry and pressure and velocity distributions.

[wyldckat]

Hi Sergey,

Please, when posting code and error outputs, please use the "[CODE]" markers, as explained in the second link of my signature. And you can edit your previous posts as well, so please add this marker to them, to make it easier to read the posts.

Regarding your question: the "*.gz" files might not be opened with success with ParaView's internal ".foam" reader. First unzip the files; on Linux, you can run this command:

find . -name "*.gz" | xargs gunzip

Then you can open the case with ParaView's internal reader.

Best regards,
Bruno

[skuznet]

Bruno, thank you for the help!
I installed ubuntu, openfoan and paraview on my homecomputer and now it works well. I can run case planeWall2d and multiRegionHeatre and can open results.
I think my previous issues with opening results were because I was opening them in Windows and files were not transferred or opened correctly in paraview under windows.

[skuznet]

Dear Bruno:

Thank you for adapting the planeWall2D.
I was able to run this case and I got some basic understanding how it works.
Based on planeWall2D tutorial I was able to set up and run a simple 3d fin case - there is a fin which is heated from the bottom and the fluid flow removes the heat from the fin. I was able to run it with air and it looks ok.

However, when I try to put water instead of air by replacing themoPhysicalProperties with file from

/chtMultiRegionFoam/multiRegionLiquidHeater/constant/bottomWater/thermophysicalProperties

:

\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      thermophysicalProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

thermoType
{
    type            heRhoThermo;
    mixture         pureMixture;
    transport       const;
    thermo          hConst;
    equationOfState rhoConst;
    specie          specie;
    energy          sensibleEnthalpy;
}

mixture
{
    specie
    {
        nMoles          1;
        molWeight       18;
    }
    equationOfState
    {
        rho             1000;
    }
    thermodynamics
    {
        Cp              4181;
        Hf              0;
    }
    transport
    {
        mu              959e-6;
        Pr              6.62;
    }
}

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

Something is going wrong. Open FOAM starts solving it but during iterations my temperature (minimal temperature in solid and in fluid domains) is reducing, which should not occur, since I have a heater.
At the end temperature in fluid domain becomes even negative, and OpenFOAM crashes.

Can you please tell me if I have to change anything else in my case when I replaced my thermophysicalProperties file with water? I guess the problem might be because thermophysicalProperties for water has different equation of state - rhoConst instead of perfectGas.

Thank you!

[wyldckat]

Hi Sergey,

A few questions:

1. Which specific multi-region solver are you using?
2. What is the flow speed for each fluid?
3. Have you checked the solid's characteristics? It might be bleeding energy due to very low or high heat transfer factors.

Best regards,
Bruno

[skuznet]

1. I'm using chtMultiRegionSimpleFoam solver, but the thermophysicalProperties file was taken from the example for chtMultiRegionFoam.

2. I have only one fluid - water, the inlet velocity is 0.1 m/s, while the size of the fin 1x1x3 m.

3. I didn't check the solid. How can I check?

The very first fluid iteration gives also very high temperature 2000, while initial temperature was 300 and temperature of the warmed surface of solid is 350:

/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.x                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.2.x-37940e0cd1ae
Exec   : /home/sergkuznet/OpenFOAM/OpenFOAM-2.2.x/platforms/linux64GccDPOpt/bin/chtMultiRegionSimpleFoam
Date   : Dec 11 2013
Time   : 16:43:49
Host   : "ubuntu"
PID    : 8592
Case   : /home/sergkuznet/OpenFOAM/run/fin2R_initial
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Disallowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create fluid mesh for region fluidDomain for time = 0

Create solid mesh for region solidDomain for time = 0

*** Reading fluid mesh thermophysical properties for region fluidDomain

    Adding to thermoFluid

Selecting thermodynamics package 
{
    type            heRhoThermo;
    mixture         pureMixture;
    transport       const;
    thermo          hConst;
    equationOfState rhoConst;
    specie          specie;
    energy          sensibleEnthalpy;
}

    Adding to rhoFluid

    Adding to UFluid

    Adding to phiFluid

    Adding to gFluid

    Adding to turbulence

Selecting turbulence model type laminar
    Adding to ghFluid

    Adding to ghfFluid

Radiation model not active: radiationProperties not found
Selecting radiationModel none
    Adding fvOptions

No finite volume options present

*** Reading solid mesh thermophysical properties for region solidDomain

    Adding to thermos

Selecting thermodynamics package 
{
    type            heSolidThermo;
    mixture         pureMixture;
    transport       constIso;
    thermo          hConst;
    equationOfState rhoConst;
    specie          specie;
    energy          sensibleEnthalpy;
}

    Adding to radiations

Radiation model not active: radiationProperties not found
Selecting radiationModel none
    Adding fvOptions

No finite volume options present

Time = 1


Solving for fluid region fluidDomain
DILUPBiCG:  Solving for Ux, Initial residual = 1, Final residual = 0.041964, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 1, Final residual = 0.0001767454, No Iterations 2
DILUPBiCG:  Solving for Uz, Initial residual = 1, Final residual = 0.0003058668, No Iterations 2
DILUPBiCG:  Solving for h, Initial residual = 1, Final residual = 0.02843725, No Iterations 1
Min/max T:299.9999 2035.089
GAMG:  Solving for p_rgh, Initial residual = 0.8476081, Final residual = 0.003588793, No Iterations 11
time step continuity errors : sum local = 0.7781759, global = -0.07076251, cumulative = -0.07076251
Min/max rho:2 2

Solving for solid region solidDomain
DICPCG:  Solving for h, Initial residual = 1, Final residual = 0.05509895, No Iterations 1
Min/max T:min(T) [0 0 0 1 0 0 0] 300 max(T) [0 0 0 1 0 0 0] 350
ExecutionTime = 1.39 s  ClockTime = 1 s

Time = 2


Solving for fluid region fluidDomain
DILUPBiCG:  Solving for Ux, Initial residual = 0.3551669, Final residual = 0.003849144, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.05855359, Final residual = 0.001012355, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 0.02422332, Final residual = 0.0003484752, No Iterations 1
DILUPBiCG:  Solving for h, Initial residual = 0.5433119, Final residual = 0.007134343, No Iterations 1
Min/max T:264.6221 2035.089
GAMG:  Solving for p_rgh, Initial residual = 0.04481994, Final residual = 0.0004256873, No Iterations 18
time step continuity errors : sum local = 3.010856, global = 1.085556, cumulative = 1.014794
Min/max rho:2 2

Solving for solid region solidDomain
DICPCG:  Solving for h, Initial residual = 0.189656, Final residual = 0.014255, No Iterations 1
Min/max T:min(T) [0 0 0 1 0 0 0] 299.7434 max(T) [0 0 0 1 0 0 0] 350
ExecutionTime = 1.92 s  ClockTime = 2 s

Time = 3


Solving for fluid region fluidDomain
DILUPBiCG:  Solving for Ux, Initial residual = 0.1454075, Final residual = 0.001948315, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.09988127, Final residual = 0.001433494, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 0.0186658, Final residual = 0.0001720673, No Iterations 1
DILUPBiCG:  Solving for h, Initial residual = 0.3185567, Final residual = 0.01199445, No Iterations 1
Min/max T:244.3615 1008.353
GAMG:  Solving for p_rgh, Initial residual = 0.2012721, Final residual = 0.001699132, No Iterations 18
time step continuity errors : sum local = 0.8901295, global = 0.2734903, cumulative = 1.288284
Min/max rho:2 2

Solving for solid region solidDomain
DICPCG:  Solving for h, Initial residual = 0.09596577, Final residual = 0.00727127, No Iterations 1
Min/max T:min(T) [0 0 0 1 0 0 0] 299.396 max(T) [0 0 0 1 0 0 0] 350
ExecutionTime = 2.44 s  ClockTime = 2 s

[skuznet]

Bruno,

I can see some inconsistency in what i'm trying to do:
the chtMultiRegionSimpleFoam in compressible solver, and in thermophysicalProperties which I used the density is constant. Can it be the reason for temperature decrease and OF crash?

[wyldckat]

Hi Sergey,

Originally Posted by skuznet

2. I have only one fluid - water, the inlet velocity is 0.1 m/s, while the size of the fin 1x1x3 m.

The fin is quite big. It's easy for it to either cool down too much or warm up too much, depending on the thermodynamic properties defined for it.

Originally Posted by skuznet

3. I didn't check the solid. How can I check?

Check the file "constant/wall/thermophysicalProperties".

Originally Posted by skuznet

The very first fluid iteration gives also very high temperature 2000, while initial temperature was 300 and temperature of the warmed surface of solid is 350:

/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.x                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.2.x-37940e0cd1ae
Exec   : /home/sergkuznet/OpenFOAM/OpenFOAM-2.2.x/platforms/linux64GccDPOpt/bin/chtMultiRegionSimpleFoam
Date   : Dec 11 2013
Time   : 16:43:49
Host   : "ubuntu"
PID    : 8592
Case   : /home/sergkuznet/OpenFOAM/run/fin2R_initial
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Disallowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create fluid mesh for region fluidDomain for time = 0

Create solid mesh for region solidDomain for time = 0

*** Reading fluid mesh thermophysical properties for region fluidDomain

    Adding to thermoFluid

Selecting thermodynamics package 
{
    type            heRhoThermo;
    mixture         pureMixture;
    transport       const;
    thermo          hConst;
    equationOfState rhoConst;
    specie          specie;
    energy          sensibleEnthalpy;
}

    Adding to rhoFluid

    Adding to UFluid

    Adding to phiFluid

    Adding to gFluid

    Adding to turbulence

Selecting turbulence model type laminar
    Adding to ghFluid

    Adding to ghfFluid

Radiation model not active: radiationProperties not found
Selecting radiationModel none
    Adding fvOptions

No finite volume options present

*** Reading solid mesh thermophysical properties for region solidDomain

    Adding to thermos

Selecting thermodynamics package 
{
    type            heSolidThermo;
    mixture         pureMixture;
    transport       constIso;
    thermo          hConst;
    equationOfState rhoConst;
    specie          specie;
    energy          sensibleEnthalpy;
}

    Adding to radiations

Radiation model not active: radiationProperties not found
Selecting radiationModel none
    Adding fvOptions

No finite volume options present

Time = 1


Solving for fluid region fluidDomain
DILUPBiCG:  Solving for Ux, Initial residual = 1, Final residual = 0.041964, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 1, Final residual = 0.0001767454, No Iterations 2
DILUPBiCG:  Solving for Uz, Initial residual = 1, Final residual = 0.0003058668, No Iterations 2
DILUPBiCG:  Solving for h, Initial residual = 1, Final residual = 0.02843725, No Iterations 1
Min/max T:299.9999 2035.089
GAMG:  Solving for p_rgh, Initial residual = 0.8476081, Final residual = 0.003588793, No Iterations 11
time step continuity errors : sum local = 0.7781759, global = -0.07076251, cumulative = -0.07076251
Min/max rho:2 2

Solving for solid region solidDomain
DICPCG:  Solving for h, Initial residual = 1, Final residual = 0.05509895, No Iterations 1
Min/max T:min(T) [0 0 0 1 0 0 0] 300 max(T) [0 0 0 1 0 0 0] 350
ExecutionTime = 1.39 s  ClockTime = 1 s

Time = 2


Solving for fluid region fluidDomain
DILUPBiCG:  Solving for Ux, Initial residual = 0.3551669, Final residual = 0.003849144, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.05855359, Final residual = 0.001012355, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 0.02422332, Final residual = 0.0003484752, No Iterations 1
DILUPBiCG:  Solving for h, Initial residual = 0.5433119, Final residual = 0.007134343, No Iterations 1
Min/max T:264.6221 2035.089
GAMG:  Solving for p_rgh, Initial residual = 0.04481994, Final residual = 0.0004256873, No Iterations 18
time step continuity errors : sum local = 3.010856, global = 1.085556, cumulative = 1.014794
Min/max rho:2 2

Solving for solid region solidDomain
DICPCG:  Solving for h, Initial residual = 0.189656, Final residual = 0.014255, No Iterations 1
Min/max T:min(T) [0 0 0 1 0 0 0] 299.7434 max(T) [0 0 0 1 0 0 0] 350
ExecutionTime = 1.92 s  ClockTime = 2 s

Time = 3


Solving for fluid region fluidDomain
DILUPBiCG:  Solving for Ux, Initial residual = 0.1454075, Final residual = 0.001948315, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.09988127, Final residual = 0.001433494, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 0.0186658, Final residual = 0.0001720673, No Iterations 1
DILUPBiCG:  Solving for h, Initial residual = 0.3185567, Final residual = 0.01199445, No Iterations 1
Min/max T:244.3615 1008.353
GAMG:  Solving for p_rgh, Initial residual = 0.2012721, Final residual = 0.001699132, No Iterations 18
time step continuity errors : sum local = 0.8901295, global = 0.2734903, cumulative = 1.288284
Min/max rho:2 2

Solving for solid region solidDomain
DICPCG:  Solving for h, Initial residual = 0.09596577, Final residual = 0.00727127, No Iterations 1
Min/max T:min(T) [0 0 0 1 0 0 0] 299.396 max(T) [0 0 0 1 0 0 0] 350
ExecutionTime = 2.44 s  ClockTime = 2 s

Then there is something very wrong with the boundary conditions.

Originally Posted by skuznet

I can see some inconsistency in what i'm trying to do:
the chtMultiRegionSimpleFoam in compressible solver, and in thermophysicalProperties which I used the density is constant. Can it be the reason for temperature decrease and OF crash?

Which specific file are you referring to? Because the file "constant/thermophysicalProperties" is not used by these multi-region solvers!

Best regards,
Bruno

[skuznet]

Bruno,

I took the file "constant/solidDomain/thermophysicalProperties" from multiRegionHeater tutorial, and it looks OK to me.

I was reffering to the file "constant/fluidDomain/thermophysicalProperties", which describes my fluid properties.

I can't find out what is wrong with this case. Could you please take a look at it?

Thank you!

[skuznet]

Dear Bruno, I've modified file fluidRegion/fvSolutions - changed rhoMin and rhoMax so that constant value of rho prescribed in thermophysicalProperties fits this interval

SIMPLE
{
    momentumPredictor on;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue       100000;
    rhoMin          rhoMin [1 -3 0 0 0] 999;
    rhoMax          rhoMax [1 -3 0 0 0] 1001;
}

Now chtMultiRegionSimpleFoam doesn't crash, but results do not look correct.

Temperature distribution in the whole model: Temperature_WholeModel_crop.jpg
Temperature in fluid domain: T_fluid_cut.jpg
Fluid velocity in fluid domain: U_fluid_cut.jpg
Pressure_rgh in fluid domain: p_rgh_fluid_cut.jpg
the case: fin2.tar.gz

The p_rgh distribution is obviously not realistic.
One can see that fluid velocity in the vicinity of top surface changes smoothly from 0 to some value, however in the vicinity of the bottom boundary such a smooth transition doesn't exist, while it should be same because the wall condition is prescribed at the top and there is fluid solid interface at the bottom, which is equivalent to wall condition.

[wyldckat]

Hi Sergey,

Sorry, I only managed to look at this today. I've had some very busy weeks.

I've done the following modifications:

diff -ur fin2_orig/system/fluidDomain/fvSolution fin2/system/fluidDomain/fvSolution
--- fin2_orig/system/fluidDomain/fvSolution    2013-11-26 20:37:33.000000000 +0000
+++ fin2/system/fluidDomain/fvSolution    2013-12-29 20:06:05.448515088 +0000
@@ -52,9 +52,9 @@
     momentumPredictor on;
     nNonOrthogonalCorrectors 0;
     pRefCell        0;
-    pRefValue       100000;
-    rhoMin          rhoMin [1 -3 0 0 0] 0.2;
-    rhoMax          rhoMax [1 -3 0 0 0] 2;
+    pRefValue       1e5;
+    rhoMin          rhoMin [1 -3 0 0 0] 999;
+    rhoMax          rhoMax [1 -3 0 0 0] 1001;
 }

If you notice, the only major difference from your latest change is the "pRefValue", where you had "100000", which is 10 times the value I have of "1e5". And "1e5" is the value used in the initial boundary conditions for the pressure fields.

Beyond this, the case is still running on my computer, so I don't if this fixed the problem or not.


edit: Something is still wrong with the pressure, because in the solid region the pressure is still set to 100000 Pa. I've stopped the simulation on my computer and will wait for feedback from your side.


Best regards,
Bruno

[skuznet]

Bruno, thank you for your answer!

I did try to run already with
rhoMin rhoMin [1 -3 0 0 0] 999;
rhoMax rhoMax [1 -3 0 0 0] 1001;
and the results do not look correct, they are shown on the previous post (#15).

regarding pressure - 100000 (five zeros) is exactly 1e5 which is athmospheric pressure, so this should be ok,

However, I discovered that in changeDictionaryDict for fluid region i misspelled the inlet patch name for temperature BC:

fron
            {
                type            fixedValue;
                value           uniform 300;
            }

while should be

front
            {
                type            fixedValue;
                value           uniform 300;
            }

Not sure I it can be the reason of strange results. Will run it again.


I don't understand the meaning of some BC used in planeWall2D and multiRegionHeater, I just copied them to my case without understanding. So not sure if I'm using them properly.

for example for velocity

U
    {
        internalField   uniform (0 0 0.1);

        boundaryField
        {
            ".*"
            {
                type            fixedValue;
                value           uniform (0 0 0);
            }
            front
            {
                type            fixedValue;
                value           uniform ( 0 0 0.1 );
            }

I prescribe fixed velocity at the incled (front) and fixed values (zeros) at the walls. But don't understand the outlet BC (back)

          back
            {
                type            inletOutlet;
                inletValue      uniform ( 0 0 0 );
                value           uniform ( 0 0 0.1 );
            }
        }
    }

How does it work?
Similar BC for temperature are used at the outlet.

I also don't understand the BC used at the fluid-solid interface.
For temperature:

"fluidDomain_to_.*"
            {
                type            compressible::turbulentTemperatureCoupledBaffleMixed;
                neighbourFieldName T;
                kappa           fluidThermo;
                kappaName       none;
                value           uniform 300;
            }

why it contains fixed value 300? It should not be fixed.

[wyldckat]

Hi Sergey,

Originally Posted by skuznet

regarding pressure - 100000 (five zeros) is exactly 1e5 which is athmospheric pressure, so this should be ok,

Sorry about that. It's really weird, because it looked like 1e6 to me every time I looked at it
Wow... now that I think about it, I did have a weird numeric mess in my mind.

Originally Posted by skuznet

I prescribe fixed velocity at the incled (front) and fixed values (zeros) at the walls. But don't understand the outlet BC (back)

          back
            {
                type            inletOutlet;
                inletValue      uniform ( 0 0 0 );
                value           uniform ( 0 0 0.1 );
            }
        }
    }

How does it work?
Similar BC for temperature are used at the outlet.

• The fixed speed set to "0" at the walls is due to the no-slip condition: http://en.wikipedia.org/wiki/No-slip_condition
• The ".*" is a regular expression for selecting all names: http://en.wikipedia.org/wiki/Regular_expression
• The fixed speed at the inlet... well, it's go to be something coming in
• As for the "inletOutlet", have a look at the User Guide: http://www.openfoam.org/docs/user/boundaries.php
  • Mmm... not much of an explanation there Essentially the "inletOutlet" and "outletInlet" boundary conditions allow you to have a valve like condition: when it's meant to flow freely, it does; when the flow is reversed, use this fixed value I'm telling you to use.
  • In this particular case, by defining "inletValue uniform ( 0 0 0 )", means that there is no reverse flow allowed. For example, if "zeroGradient" was used and in case for whatever reason there is a vortex building up and going out the outlet, it would lead to having fluid flowing outside and coming back in, through the same patch. With the configured "inletOutlet", this is not allowed.
  • The "value" entry for "inletOutlet" is used only as the initial value. After the first iteration, it's always the result of the simulation.

Originally Posted by skuznet

I also don't understand the BC used at the fluid-solid interface.
For temperature:

"fluidDomain_to_.*"
            {
                type            compressible::turbulentTemperatureCoupledBaffleMixed;
                neighbourFieldName T;
                kappa           fluidThermo;
                kappaName       none;
                value           uniform 300;
            }

why it contains fixed value 300? It should not be fixed.

In this case, the "value" entry is also only the initial value. It would only be a fixed value if the "type" of the boundary condition was "fixedValue".


Did you go properly study the tutorials in the User Guide? Or did you just go through them as fast as you could?

Best regards,
Bruno

[skuznet]

Bruno, thanks for explanation.

In tutorial http://www.openfoam.org/docs/user/boundaries.php
inletOutlet and solid-surface BC are not well detailed, your explanation is better.

I fixed the misspelled patch name and run case again. But result still doesn't look correct, in fact it became even worse - I don't see anymore temperature variation inside fluid domain, only on boundaries.

Can you please explain to me also the pressure BC?

p_rgh
    {
        internalField   uniform 1e5;

        boundaryField
        {
            ".*"
            {
                type            fixedFluxPressure;
                value           uniform 1e5;
            }

            back
            {
                type            fixedValue;
                value           uniform 1e5;
            }
        }
    }

    p
    {
        internalField   uniform 1e5;

        boundaryField
        {
            ".*"
            {
                type            calculated;
                value           uniform 1e5;
            }

            back
            {
                type            calculated;
                value           uniform 1e5;
            }
        }
    }

[wyldckat]

Quoting Tobi:

Originally Posted by Tobi

p = total pressure
p_rgh = p - rho *gh (total pressure - hydrodynamic pressure)

You can learn more about any boundary conditions here: http://foam.sourceforge.net/docs/cpp/modules.html


I ran the simulation for 1600 iterations and it seems that the fluid part is highly efficient in either absorbing heat or very efficient at running away from it

Two questions:

1. Do you know the analytical solution to this? More specifically, what's the analytical solution of the temperature profile, for an infinite wall scenario, where the water is running at 0.1 m/s and exposed to the heated wall for 30s?
2. Why is the simulation running in laminar mode? Because in laminar mode, you do not have a turbulent mixing layer.
3. Have you tried increasing the number of cells near the wall, so that you can get a better accuracy in the results near the wall?