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integral of the gradient of a variable over a face during unsteady simulation

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Old   December 19, 2017, 23:52
Default integral of the gradient of a variable over a face during unsteady simulation
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Bingchuan
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Hi All,

I want to get the integral of the gradient of a variable (e.g. Temperature) over a face during doing an unsteady simulation.

1. First, I computed the gradient of the variable by adding the following code into the main function of the solver, then it is compiled.

Code:
         volVectorField gradT(fvc::grad(T));

 

         volScalarField gradTx

         (

             IOobject

             (

                 "gradTx",

                 runTime.timeName(),

                 mesh,

                 IOobject::NO_READ,

                 IOobject::AUTO_WRITE

             ),

             gradT.component(vector::X)

         );

 

         volScalarField gradTy

         (

             IOobject

             (

                 "gradTy",

                 runTime.timeName(),

                 mesh,

                 IOobject::NO_READ,

                 IOobject::AUTO_WRITE

             ),

             gradT.component(vector::Y)

         );

 

         volScalarField gradTz

         (

             IOobject

             (

                 "gradTz",

                 runTime.timeName(),

                 mesh,

                 IOobject::NO_READ,

                 IOobject::AUTO_WRITE

             ),

             gradT.component(vector::Z)

         );
The gradTx, gradTy and gradTz are wrote in the time series directories. Of course I can get the integral of gradT over a face in the post-process software (e.g. paraView). However, since the computational domain is large, it is inpossilbe to to write gradT in small time interval. So I have to find another way out.

2. I planed to use the function objects. I put the patchIntegrate file in the system directory of my case, which was included by the controlDict file. The item fields in the patchIntegrate file are defined as
Code:
fields (U  gradT)
or
Code:
fields (U gradTx)
However, only integral of U over the patch were outputted successfully. No integral of gradT or gradTx such data was wrote.

3. Then I tried the singleGraph in the same way as patchIntegrate.

No gradT or gradTx such data was wrote along the line I defined neither.

Is there anyone knows how to solve this problem or anyone has better strategy to do this? Thank you very much.

kind regards,
Bingchuan
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Old   December 20, 2017, 04:46
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Bingchuan
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Can anyone bring me a ray of light?
many Thanks.
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Old   December 20, 2017, 06:06
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Agustín Villa
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Hi

can you show us the case folder? At least, the controlDict file.

Quote:
it is inpossilbe to to write gradT in small time interval
what do you mean there?
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Old   December 21, 2017, 06:19
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Bingchuan
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Dear Agustin,

Thanks for your reply.

Below is the information of my transient simulation.
1. Code added into the main function of the solver
Code:
....
  volVectorField gradT(fvc::grad(T));

 

         volScalarField gradTx

         (

             IOobject

             (

                 "gradTx",

                 runTime.timeName(),

                 mesh,

                 IOobject::NO_READ,

                 IOobject::AUTO_WRITE

             ),

             gradT.component(vector::X)

         );
....
2. The controlDict file:
Code:
....

timeFormat      general;

timePrecision   6;

runTimeModifiable true;

adjustTimeStep  no;

maxCo           0.5;

// ************************************************************************* //
functions
{
/#includeFunc patchIntegrate
}
3. The patchIntegrate file
Code:
name   Mypatch;
fields ( U T gradT gradTx);
operation areaIntegrate;

type            surfaceRegion;
libs            ("libfieldFunctionObjects.so");
regionType  patch;

writeControl    timeStep;
writeInterval   1;
...
Goal: output the integral of fields U, T, gradT and gradTx over the given patch at every timestep using the function object patchIntegrate.

Issue: Integrals of fields U and T at every timestep have been outputted successfully. However, It is failed to output the integral of gradT and gradTx.

log information: FOAM warning: From function Foam::label Foam::sampledSets::classifyFields() in file sampledSetsGrouping.C at line 140 cannot find registered field matching gradT. (The same warning for gradTx)

Thanks.

Bests,
Bingchuan
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