A criterion for interrupting an evolution scheme is based on the values of a field
in a domain 
. The set of values of 
in the domain 
will be noted as 
.
Important: Note that though fields can be either a vector or a scalar, for the sake of
simplicity they will always be denoted as 
in this section and the sections that follow.
If the field is not a scalar, you have to use a restriction function
to convert the non-scalar value to a scalar one, which is then
called the restricted value and noted 
. The subscript 
refers to the node index.
The value to check is obtained by applying a function 
on the restricted value 
or 
.
Eventually, an inequality test 
is applied to check the value of the field with respect to a limit
.
Thus, a criterion is written has follows:
 | (28–1) |
For the criteria 
:
the field is temperature on the domain
: 
there is no restriction function,
the function for obtaining the check value is the minimum,
the inequality test is "less than".
For the criteria 
:
the field is velocity along the wall:
the restriction function is the norm:
the function for obtaining the check value is the minimum,
the inequality test is "less than".