calculate burnout using post along tracks
 

Hi, I am working on coal combustion simulation using Lagrangian. The next step is to calculate Burnout, defined as (1-mfa0/mfa)/(1-mfao). When I introduce this into "Expression" in CFXPOST, an error information appears as

" INTERNAL [internal error detected:] Number of values in retrieved variable does not match number of vertices "

Burnout should be calculated based on track variables or field variables? Have anyone have such experience or knowledge?

I need your help urgently. Pls reply or contact me by (ben.simpsons@gmail.com). Thanks in advance.

Ben