- provides a simple means of defining/modifying fields. For example,
```
<name1>
{
type exprField;
libs (fieldFunctionObjects);
field pTotal;
expression "p + 0.5*(rho*magSqr(U))";
dimensions [ Pa ];
}
```
It is is also possible to modify an existing field.
For example, to modify the previous one.
```
<name2>
{
type exprField;
libs (fieldFunctionObjects);
field pTotal;
action modify;
// Static pressure only in these regions
fieldMask
#{
(mag(pos()) < 0.05) && (pos().y() > 0)
|| cellZone(inlet)
#};
expression "p";
}
```
To use as a simple post-process calculator, simply avoid storing the
result and only generate on write:
```
<name2>
{
store false;
executionControl none;
writeControl writeTime;
...
}
```