kntu civil engineerig faculty ` flow in pipes with special thanks to mr.vakilzade
TRANSCRIPT
For pipes of constant diameter and incompressible flow
Vavg stays the same down the pipe, even if the velocity profile changes
same
Vavg Vavg
samesame
Conservation of Mass
For pipes with variable diameter, m is still the same (due to conservation of mass),
but V1 ≠ V2
D2
V2
2
1
V1
D1
m m
Consider a round pipe of diameter D. The flow can be
laminar or turbulent. In either case, the profile develops
downstream over several diameters called the entry
length Lh. Lh/D is a function of Re.
or
cancel (horizontal pipe)
V1 = V2, and 1 = 2 (shape not changing)
hL = irreversible head loss & it is felt as a pressuredrop in the pipe
Energy equation (in head form):
But for laminar flow, roughness does not affect the flow unless it is huge
Laminar flow: f = 64/Re
Turbulent flow: f = Moody Chart
Energy Line (EL) and Hydraulic Grade Line (HGL)
(Source: Larock, Jeppson and Watters, 2000: Hydraulics of Pipeline Systems)