Move the equation latex to a seperate place, where it can be refered
by serevel places.

The formula to compute this can be found in paper of Junk 2005
after equation A.15
where is the second velocity moment,
is the identity matrix and .\n
Note that is not shear rate yet.

\todo: this section can become a function that be called by several
places.

Nodes of different colours represent the following:

Solid arrows point from a procedure to one which it calls. Dashed
arrows point from an interface to procedures which implement that interface.
This could include the module procedures in a generic interface or the
implementation in a submodule of an interface in a parent module.

Nodes of different colours represent the following:

Solid arrows point from a procedure to one which it calls. Dashed
arrows point from an interface to procedures which implement that interface.
This could include the module procedures in a generic interface or the
implementation in a submodule of an interface in a parent module.