[Mojtaba.a]

Hi guys.

Ok, I already know that I can use the following code and compute the mag of U easily:

postProcess -func "mag(U)"

There is a big but here. Checkout this command:

postProcess -fields "(p U)" -func wallShearStress

It is mentioned in the OpenFOAM user guide and it works just fine. I guess you guess what my question is now; why I cannot get the mag of U by the following command:

postProcess -field U -func mag

It gives me the following error:

Time = 1

Reading fields:
    volVectorFields: U

Executing functionObjects
--> FOAM Warning :     functionObjects::mag mag cannot find required object <fieldName> of type volScalarField
--> FOAM Warning :     functionObjects::mag mag cannot find required object <fieldName> of type surfaceScalarField
--> FOAM Warning :     functionObjects::mag mag cannot find required object <fieldName> of type volVectorField
--> FOAM Warning :     functionObjects::mag mag cannot find required object <fieldName> of type surfaceVectorField
--> FOAM Warning :     functionObjects::mag mag cannot find required object <fieldName> of type volSphericalTensorField
--> FOAM Warning :     functionObjects::mag mag cannot find required object <fieldName> of type surfaceSphericalTensorField
--> FOAM Warning :     functionObjects::mag mag cannot find required object <fieldName> of type volSymmTensorField
--> FOAM Warning :     functionObjects::mag mag cannot find required object <fieldName> of type surfaceSymmTensorField
--> FOAM Warning :     functionObjects::mag mag cannot find required object <fieldName> of type volTensorField
--> FOAM Warning :     functionObjects::mag mag cannot find required object <fieldName> of type surfaceTensorField
--> FOAM Warning :     functionObjects::mag mag failed to execute.

What are the differences?

Cheers & Stay Healthy!

[zhangyan]

You need a configuration file in the system directory, like this:
https://github.com/OpenFOAM/OpenFOAM...ing/fields/mag
change the <fieldName> to U

and then:

postProcess -func mag -field U

finally, you will get mag(U) in the $time directory.

[Mojtaba.a]

Originally Posted by zhangyan

You need a configuration file in the system directory, like this:
https://github.com/OpenFOAM/OpenFOAM...ing/fields/mag
change the <fieldName> to U

and then:

postProcess -func mag -field U

finally, you will get mag(U) in the $time directory.

Thank Yan,

But I already have the configuration file in the OpenFOAM caseDicts directory. However, I copied the file into my system folder too:

foamGet mag

I tried the command but again the same error happened.

Cheers

[zhangyan]

Don't forget to change the <fieldName> to U

[Mojtaba.a]

Originally Posted by zhangyan

Don't forget to change the <fieldName> to U

Yea, that did the trick. Thanks!

However, I get two warnings whenever I try to compute mag(U) field using any method. Do you know why?

Time = 1

Reading fields:
    volVectorFields: U

Executing functionObjects
--> FOAM Warning :     functionObjects::mag mag cannot find required object U of type volScalarField
--> FOAM Warning :     functionObjects::mag mag cannot find required object U of type surfaceScalarField
    functionObjects::mag mag writing field: mag(U)

[zhangyan]

Me too. Just forget it.