[marluc]

Dear all,

I want to write the an average field on two patches, namely inlet and outlet of a duct, using the functionObject patchAverage from swak4Foam.

The code I entered in controlDict file is the foloowing:

velAreaWeightAvg
       {
        type patchAverage;
        verbose true;
         fields
           (
               Uz
           );
         patches
           (
            inlet
             outlet
           );
         factor 1.0;
         outputControlMode   outputTime;
         outputInterval    1;
         allowCoupled true; // because the patches are cyclic coupled
       }

I always get the following warning message, independently from the field I want to average, and neither is a file written into the corresponding directory nor do I get printed values on the screen:

--> FOAM Warning : 
    From function probes::read()
    in file patch/patchFieldFunctionObject/patchFieldFunctionObject.C at line 100
    Unknown field Uz when reading dictionary ".patchAverage"
    Can only probe registered volScalar, volVector, volSphericalTensor, volSymmTensor and volTensor fields

Time = 17000
    Operating in no-flow mode; no models will be loaded. All vol, surface and point fields will be loaded.
Reading volScalarField Uz
Reading volScalarField Uy
Reading volScalarField nut
Reading volScalarField Ux
Reading volScalarField p
Reading volScalarField k
Reading volScalarField epsilon
Reading volVectorField wallShearStress
Reading volVectorField U
Reading surfaceScalarField phi

Could you please explain me my (probably stupid) mistake?

Thank you in advance,
Luca

[gschaider]

Originally Posted by marluc

Dear all,

I want to write the an average field on two patches, namely inlet and outlet of a duct, using the functionObject patchAverage from swak4Foam.

The code I entered in controlDict file is the foloowing:

velAreaWeightAvg
       {
        type patchAverage;
        verbose true;
         fields
           (
               Uz
           );
         patches
           (
            inlet
             outlet
           );
         factor 1.0;
         outputControlMode   outputTime;
         outputInterval    1;
         allowCoupled true; // because the patches are cyclic coupled
       }

I always get the following warning message, independently from the field I want to average, and neither is a file written into the corresponding directory nor do I get printed values on the screen:

--> FOAM Warning : 
    From function probes::read()
    in file patch/patchFieldFunctionObject/patchFieldFunctionObject.C at line 100
    Unknown field Uz when reading dictionary ".patchAverage"
    Can only probe registered volScalar, volVector, volSphericalTensor, volSymmTensor and volTensor fields

Time = 17000
    Operating in no-flow mode; no models will be loaded. All vol, surface and point fields will be loaded.
Reading volScalarField Uz
Reading volScalarField Uy
Reading volScalarField nut
Reading volScalarField Ux
Reading volScalarField p
Reading volScalarField k
Reading volScalarField epsilon
Reading volVectorField wallShearStress
Reading volVectorField U
Reading surfaceScalarField phi

Could you please explain me my (probably stupid) mistake?

Thank you in advance,
Luca

Which utility are you using? The problem is that at the time of construction/reading of the functionObject the field is not present in memory. The swak-utilities replayTransientBC and funkyPythonPostproc offer for that situation a entry "preloadFields" to make sure that the fields are in memory when the functionObjects are loaded.

[marluc]

Dear Bernhard,

first of all thank you very much for your quick reply.

I want to obtain an area weighted average value of some variables and therefore I opted for patchAverage from libSimpleFunctionObjects, as described at the following link:
http://openfoamwiki.net/index.php/Co...unctionObjects

Now I managed to solve the problem using the following code:

velAvg2
    {
        type patchExpression;
        variables 
            ( "UzAvg{patch'inlet}=sum(Uz*area())/sum(area());" );
        accumulations (
           min
           max
        );
        patches (
            inlet
        );
        expression "UzAvg";
        verbose true;
        allowCoupled true;
    }

I derived the above procedure from here: http://openfoamwiki.net/index.php/Co...sureDifference

Could you please make an example of how using the replayTransientBC and/or funkyPythonPostproc to "preload" the necessary fields for my problem?

Thank you very much in advance.
Luca

P.S. I forgot to point out that I installed swak4Foam for OF 2.3.0

[gschaider]

Originally Posted by marluc

Dear Bernhard,

first of all thank you very much for your quick reply.

I want to obtain an area weighted average value of some variables and therefore I opted for patchAverage from libSimpleFunctionObjects, as described at the following link:
http://openfoamwiki.net/index.php/Co...unctionObjects

Now I managed to solve the problem using the following code:

velAvg2
    {
        type patchExpression;
        variables 
            ( "UzAvg{patch'inlet}=sum(Uz*area())/sum(area());" );
        accumulations (
           min
           max
        );
        patches (
            inlet
        );
        expression "UzAvg";
        verbose true;
        allowCoupled true;
    }

I derived the above procedure from here: http://openfoamwiki.net/index.php/Co...sureDifference

Could you please make an example of how using the replayTransientBC and/or funkyPythonPostproc to "preload" the necessary fields for my problem?

Thank you very much in advance.
Luca

P.S. I forgot to point out that I installed swak4Foam for OF 2.3.0

OK. But before we go on: WHICH utility/solver do you use? You only give inputs and part of the output but leave us in the dark about that. functionObjects live in the context of a solver and without that context everything is guesswork.

[marluc]

Dear Bernhard,

I am sorry...you're perfectly right...I am using simpleFoam (actually a modified version that includes a constant pressure drop source term).
I use cyclic BC at the inlet and outlet patches of the duct. Here follows my controDict entries:

FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

libs (
      "libOpenFOAM.so"
      "libsimpleSwakFunctionObjects.so"
      "libswakFunctionObjects.so"
      "libgroovyBC.so"
     );

application     simplePeriodicP; // based entirely on simpleFoam

startFrom       startTime;

startTime       1;

stopAt          endTime;

endTime         20000;

deltaT          1;

writeControl    timeStep;

writeInterval   5;

purgeWrite      5;

writeFormat     ascii;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;

functions
(   
       patchAverage
       {
        type patchAverage;
        verbose true;
         fields
           ( Uz );
         patches
           (
            inlet
            outlet
           );
         factor 1.0;
         outputControlMode   outputTime;
         outputInterval    1;
         allowCoupled true;
       }
);

Thank again for your help.
Luca

[gschaider]

Originally Posted by marluc

Dear Bernhard,

I am sorry...you're perfectly right...I am using simpleFoam (actually a modified version that includes a constant pressure drop source term).
I use cyclic BC at the inlet and outlet patches of the duct. Here follows my controDict entries:

FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

libs (
      "libOpenFOAM.so"
      "libsimpleSwakFunctionObjects.so"
      "libswakFunctionObjects.so"
      "libgroovyBC.so"
     );

application     simplePeriodicP; // based entirely on simpleFoam

startFrom       startTime;

startTime       1;

stopAt          endTime;

endTime         20000;

deltaT          1;

writeControl    timeStep;

writeInterval   5;

purgeWrite      5;

writeFormat     ascii;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;

functions
(   
       patchAverage
       {
        type patchAverage;
        verbose true;
         fields
           ( Uz );
         patches
           (
            inlet
            outlet
           );
         factor 1.0;
         outputControlMode   outputTime;
         outputInterval    1;
         allowCoupled true;
       }
);

Thank again for your help.
Luca

Uz is something you added in that modified solver. My guess ist the following: You added that field AFTER the time-loop is started. That's why one finds it and the other doesn't. The order of things is the following

1. usual fields are created in createFields.H
2. time-loop starts. The functionObjects are initialized. patchAverage doesn't find Uz in memory and removes it from the list (warning)
3. Uz gets created (or read)
4. Usual time-step calculations
5. patchExpression is evaluated. It finds Uz in memory and therefor produces a result