It is used to define the velocity field \(\bu_\text{given}\) when the Navier-Stokes equations are not approximated. Moreover, in the data file the following line has to be set to false:

===Restart on velocity (true/false)

If it set to true, the velocity is read from a suite file of the Navier-Stokes equations and not this function.

This function defines a time independent velocity field for one given Fourier mode on all of the nodes of the finite element mesh.

Inputs and outputs

The inputs of this function are the following:

m is the Fourier mode \(m\) considered. It is an integer.
H_mesh is the finite element mesh used to approximate the magnetic field.

The output of this function is a real valued tabular vv of dimension (H_mesh%np,6).

Exemple

Here is an exemple where we set \(\bu_\text{given}=r\textbf{e}_\theta\) where \(\textbf{e}_\theta\) is the unit vector in the azimuthal direction.

The corresponding code lines are written as follows.

IF (TYPE==3.AND.m==0) THEN
   vv = rr(1,:)
ELSE
   vv = 0.d0
END IF
RETURN

Remark: The divergence of the velocity field has to be zero.

We refer to the sections Examples with manufactured solutions and Examples on physical problems for more examples.