convergence acheived but problem
 

i tried to simulate laminar flow in a small pipe of dia 5mm and length 26cm and the solution.
inlet vel 0.06m/s
the pressure drop i am getting is 8pa
but if u calculate analiticaly we get 20pa
i dont understand where i am wrong
please reply

what is your fluid? if your fluid is water, it cause because it needs more length to become fully developed.

thank you very much
it didnt strike my head
thank you