[tayo]

Hello,
I'm puzzled about the way openfoam computes the gradient scheme. I have a temperature field, T that varies between 358 - 400K and I simply take the gradient using fvc::grad(T), with Gauss linear scheme. With a mesh size is approx. 0.3 mm, some of the results for the gradient are printed below:

const volScalarField& T = alpha1_.db().lookupObject<volScalarField>("T");
volVectorField gradT = fvc::grad(T);
Info << "gradT =" << gradT << endl;
(-164633 -164633 0)
(0 -164633 0)
(0 -164633 -2.98156e-10)
(0 -164633 -2.98156e-10)
(0 0 2.98156e-10)
(0 0 1.49078e-10)
(164633 -164633 0)
(0 0 0)
(0 0 0)
(164633 0 0)
(0 0 0)
 :  :  :
 :  :  :

Some of my basic questions are:
1.) Why does it print out negative numbers?
2.) How does it get gradient values of (0 0 0) when the T values vary between 358 - 400K.
3.) Why is the z- gradient values so low (2.98156e-10) considering the small mesh size?
Kindly help explain what's happening here. Thanks