The pressure-correction method as implemented in the ISNaS incompressible
code is the one described in Van Kan et al. (1991). Starting point is the
-method formulated by (8.4), (8.5) or the variant
(8.8), (8.9).
Following Van Kan et al. (1991) we define an intermediate velocity 
by:
must be such that the boundary conditions at 
are satisfied. In the case of prescribed normal velocities
this means that the corresponding rows in the matrix G contain
zeros.
Subtraction of (9.2) from (8.8) gives
where the term 
has been
neglected.
Application of (8.9) to
(9.3) gives
which is a Laplacian-type equation for the pressure correction. Once
has been computed 
follows from
(9.3):
Remark: the matrix 
is in general
non-symmetrical.
