[sagar_saroha]

I have been using:

pisoFoam -postProcess -func "grad(U)"

and it works well... but when i try using:

pisoFoam -postProcess -func "grad(UMean)"

for calculating mean velocity gradient - it show the following error


--> FOAM Warning : functionObjects::grad grad(UMean) cannot find required object UMean of type volScalarField
--> FOAM Warning : functionObjects::grad grad(UMean) cannot find required object UMean of type surfaceScalarField
--> FOAM Warning : functionObjects::grad grad(UMean) cannot find required object UMean of type volVectorField
--> FOAM Warning : functionObjects::grad grad(UMean) cannot find required object UMean of type surfaceVectorField
--> FOAM Warning : functionObjects::grad grad(UMean) failed to execute.

Please help me identify the mistake or suggest an alternate way to calculate gradient of mean velocity.

[sagar_saroha]

In my attempts to solve the problem, I managed to get an alternate way of doing so...
Seemingly the problem was mainly due to the name of the file 'UMean'. I did rename the file to 'U' and then calculated its gradient using

pisoFoam -postProcess -func "grad(U)"

I still expect to hear from experienced users about the non-eluding way of addressing it.

[kera]

Hallo Sagar!

If you already have your simulation results of the case!

Can you tell me, what output do you get after executing this piece of command in the terminal:

postProcess -latestTime -func "grad(UMean)" 

or 

postProcess -noZero -func "grad(UMean)"

or if you wanna re-run the simulation, try executing with the command, (I am not sure about this one):

pisoFoam -postProcess -noZero -func "grad(UMean)"

Regards,
Ricky

PS: I am assuming that the UMean field exist in your time directories

[sagar_saroha]

Hi Ricky

Thanks a lot for the reply; both of your suggestions do work:

Originally Posted by kera

postProcess -latestTime -func "grad(UMean)" 

or 

postProcess -noZero -func "grad(UMean)"

PS: I am assuming that the UMean field exist in your time directories

yeah, I had UMean field existing in the time directories.

I am curious to know if it was 'zero' time folder which was causing issue or something else?

[kera]

Hallo Sagar!

well your suspicion is in fact correct. It was actually the "zero" folder that was causing the error, as "UMean" field is not available at the start, rather it is created in the subsequent iterations. --> at least that's what I think

Regards,
Ricky

Originally Posted by sagar_saroha

I am curious to know if it was 'zero' time folder which was causing issue or something else?

[JM27]

Hello,


I know this post is a bit old but it's the only one I could find that prints a similar error message to what I'm getting.

I am also using OF v5 and I introduced a functionObject in my controlDict to calculate the gradient of velocity during run-time using grad(U).

The functionObject is:

gradUtensor// shearStressU // originally gradientU
       {
        type             grad;
        libs             ("libfieldFunctionObjects.so");
        field            U;
        writeControl     writeTime;

       }

and the warning that is printed in the log file is:

--> FOAM Warning :     functionObjects::grad gradUtensor cannot find required object U of type volScalarField
--> FOAM Warning :     functionObjects::grad gradUtensor cannot find required object U of type surfaceScalarField

I've tried changing the name of the function and I have also tried the postProcess option using -noZero and -latestTime flags on a different case and I still get a similar error. The grad(U) is computed but I am not sure why the WARNING continues to be printed? Am I missing something?