How to obtain a wall normal vector that can be used in a solver CEL expression?
In the CFX solver the wall normal variables Normal X etc. are not available for CEL expressions. However, this vector is required if you are interested i.e. in computing a wall tangential velocity i.e. on a moving bent belt. Steps to obtain the wall normal vector for CEL: 1. run a simulation without the wall velocity specified for 1 time step 2. open the result file in CFDPost 3. export the Normal X, Normal Y, Normal Z variables into a csv file 4. modify the csvfile to a profile file format 5. open CFXPre and load the csvfile as profile data 6. Now the variables are available as functions and can be used in CEL expressions. For the example of a moving belt, a wall tangential vector can be calculated from the wall normal vector. Normalizing is and multiplying with the constant belt velocity provides a wall tangential velocity that is always tangential to the wall and has the correct magnitude. 

