calculation of a variable's average on a normal line to a surface's point
 

Good day everyone,

my problem is this:
I have a tube inside of another tube. This is filled with water. I want to know the mean average of a substance that is located upon a virtual normal line to the inner tube's surface in every point of its surface.

This will be challenging in CFD-Post. I would use a high-end post processing package like Fieldview, Ensight or Tecplot to do this.