 Donor cell scheme: constant within each cell
 Improvement:
piecewise linear method
(PLM):
reconstruction by linear function in each cell
Once we know the cell average
and the slope
,
we get the flux over
from

(147) 
If the boundary value in the cell is used for the entire cell we get

(148) 
For
we get from each cell
the flux
.
For
we get from each cell
the flux
.