Guidelines for the use of “a” and “the.”
The words “a” and “the” are easily mixed.
The word “a” can be viewed as reference to a general procedure or method.
Unfortunately “the” can play the same role. But following some use guidelines can reduce the confusion.
The “a” refers to an approach and implies that an application of finite element mathematics was used to solve the problem and “the” refers to the specific (solved) problem of describing flow next to “the” (again specific) surface.
So generally try to use “a” for a general relation and “the” for a specific relation.
