question about createField
 

hello
I'm new user and I want to know what the statement "mesh" do in this lines:

volScalarField u
(
IOobject
(
"u",
runTime.timeName(),
mesh,
IOobject::MUST_READ,
IOobject::AUTO_WRITE,
),
mesh
)

I want to do some change into some area of a mesh like specify u in a plane or specific region can changing the "mesh" in here help me?

you should use the setFields utility together with setFieldsDict. This will allow you to change the values of any variable you solve for. Have a look at the multiphase tutorial for an example of what setFields can do.