happy

yeah..

I am happy for no specific reason.

Everyone should feel comfortable on doing anything.

fully developed flow pipe length

DL=dimensionless length=length/diameter
laminar
  DL=0.06Re
turbulent
  DL=4.4(Re)^1/6

http://www.engineeringtoolbox.com/entrance-length-flow-d_615.html

歪掉了.....

drawing