[babakflame]

Dear Fellows

I have few questions regarding the following snippet:

scalar ULeft = 0.0;
label leftI = mesh().boundaryMesh().findPatchID("left");
const fvPatchVectorField& fvp = U.boundaryField()[leftI];
if (fvp.size())
{
ULeft = fvp[0].x();
}
reduce(ULeft, maxOp<scalar>());

After labeling leftI, the 3rd line puts the velocity of the "left" ptach into fvp "object".
I assume the size of fvp is non-zero, so the "if" loop executes.
My first question is on

ULeft = fvp[0].x();

.
here, fvp is an array of vectors, since it keeps the velocity vectors of a patch, but the above command just stores the first component ".x()" of first vector "[0]" in the array of vectors. Am I correct?

For example assume
fvp = { (1 2 3) (4 5 6) (7 8 9)}
then fvp[0].x means 1
then why using the

reduce(ULeft, maxOp<scalar>());

command?

I assume that reduce() function with maxOp<scalar> finds the biggest scalar in an array of scalars, but here ULeft just has one member!!! (in my example 1)

Am I missing sth?


Regards