How to use swakeFoam to implement volume average
 

hi everyone!

i want to use the swakeFoam to volumeAverage a scalefield "Cc"， then probe it，

i insert the code are as follows,

Cc_average
{
type expressionField;
autowrite true;
expression "volumeAverage(Cc)";
dimension [0 0 0 0 0 0 0];
outputControl timeStep;
outputInterval 200;
fieldName Cc_average;
}

but it doesn't work

how can i solve this problem?