[Mojtaba.a]

Hi,
I am using simpleFunctionObject to average some fields in volume. I can do this for simple filelds like T. for instance I add the following code into controlDict file:

functions
(
temp_average
{
type volumeAverage;
functionObjectLibs
(
"libsimpleFunctionObjects.so"
);
verbose true;
fields (T);
}
);

But I don't know how to to do this for total velocity magnitude. When I use U instead of T in above code, I get average volume of velocity vector. I need average velocity magnitude.
How can I do that? any suggestions?