Question about field defintion
 

I have a question concerning the definition of fields, either vectorial or tensorial, for CFD calculations. In
particular, during my calculations I have to calculate the gradient of velocity field, by defintion a volVectorField,
using the formula

DU = fvc :: grad (U);

Both DU and U are defined in the file createFields.H, in the following form

// Reading the velocity field

Info<< "Reading field U\n" << endl;
volVectorField U
(
IOobject
(
"U",
runTime.timeName(),
mesh,
IOobject::MUST_READ,
IOobject::AUTO_WRITE
),
mesh
);

Info<< "Creating Velocity Gradient Tensorial Field\n" << endl;
volTensorField DU
(
IOobject
(
"DU",
runTime.timeName(),
mesh,
IOobject::NO_READ,
IOobject::NO_WRITE
),
fvc::grad(U)
);

This way, I ensure that in each mesh point I calculate correctly DU, right?

Other form could be doing the following

volTensorField DU = fvc :: grad ( U() );

I believe the first form is correct, although the second may work. Can anybody help me out?

Regards,

Titio

Dear Titio,

Both forms are possible and the second will work if you delete the brackets on U.

volTensorField DU = fvc::grad (U);

Henrik