[ooo]

I would like to set/get the velocity of the nodes of a simple Cartesian grid by a simple loop to be able to do some interpolation of them(and put the interpolated value into an user-defined vector!)
For example i would like to store/change the velocity by these kind of loops :

for (indices i = 1 ; i < ... ; ++i) {
u(indices of a particular node) = 0 ; //Setting value...
double a = u(indices of a particular node);} //Getting value...

I would appreciate if you tell me how can i find the index of nodes.
For example, this code(mesh.findCell(point(x, y, z)); ) gives the index of the nearest cell, but i need to have an overview of the index of all cells(e.g to be able to iterate through them with a for loop).
Also i don't know whether with the below code, can i SET the velocity of the index? or it is just a getter function? : U.mesh().C()[Index].x();

[Bernhard]

What do you exactly want?

Anyhow, you might be looking for the forAll loop that comes with OpenFOAM. Structure looks something like this

 forAll(U, cellI)
 { 
    U[cellI] = ...
 }