how to fit outlet velocity profile
 

Sir
I am doing a basic laminar tutorial of pipeflow in fluent.i got a outlet velocity profile.to check whether it is exactly parabolic or not, i used excel but excel is not taking exact curve.forecasted curve is deviating from curve which is obtained from output data.so please explain how to check the obtained outlet profile is exactly parabolic or not. even in case of turbulent also i am getting the same problem.