[maybee]

hi,

I have read:

http://www.openfoam.org/docs/user/mesh-description.php

Questions:
1. The boundary mesh are the faces of the outer cells that together build the border of the geometry?

2.
Out of the link above:

The boundary is required to be closed, i.e. the sum all boundary face area vectors equates to zero to machine tolerance.

What does the example given in this sentence mean?

[ngj]

Hi Maybee,

Ad. 1: Yes.

Ad. 2: It simply means that you need to mesh the entire volume, which you consider, and you are not allowed to have overlapping faces.
I.e. you would not consider a football to be closed, if you put a hole in it. The sum of the surface normal vectors on a closed football is per definition 0, but with the whole (only consider the outside of the ball for the sake of the argument), you will have an error, which is of the size of the area of the hole.

Kind regards,

Niels

[maybee]

hi,

thx.

sum of the surface normal vectors

"surface normal vectors" made it much clearer to me. Furthermore I just was not sure if the sum of them would be 0 in every geometry.