The dose conservation criterion compares the quantity's local dose error
with its total dose in the computational domain. The total dose 
is
obtained from (3.6-13) where 
is the concentration of
quantity 
at grid point 
and 
is the cell area associated
with grid point (see Figures 3.4-3 and 3.4-6).
We get the grid criterion 
(3.6-14) for a grid line at the
vertical position 
by adding up the local dose error along this
grid line in lateral direction (see Figure 3.6-2).
In (3.6-14) 
and 
denote the number of grid lines in
vertical and lateral direction, respectively. 
is the number of
different quantities which are resolved by the grid, and 
is
accuracy parameter. An analogous expression is used as the criterion for a
grid line at a lateral position 
.
The criterion 
is used to decide if grid lines have to be
inserted in the vicinity of vertical position . If this grid line were
deleted, the dose error would be 
(3.6-15). This
criterion is applied to decide if the grid line may be deleted.
