How To recall previous positions ?
 

Hello Everyone, I've been looking on the forum but obiously noOne has ever wanted to do that.

I am currently writing a UDF to store the position of the maximun vorticity of a pair of vortex in ground effect so that i can draw their trajectory. It works well, I am storing the position of the max vorticity in a txt file but Now I want to recall the last position so I can tell Fluent where to search for the next position.

I ve been trying to get the velocity at the previous time step in order to discretize itbut I don't know how to, is it right to do C_V(c+1,t)-C_V(c-1,t)/2DX ?/
Thank you very much

Alex