**Unformatted text preview: **Tutorial 7 : laminar and turbulent flow
Covers week 6 and 7 lecture material
Elger / Crowe et al Chapter 10
Problem ]
A liquid is pumped through a $60 - mm- diameter pipe at a flow rate of 0. 0002 m' / s. Calculate the
pressure drop in a 10 - m horizontal section if the liquid is :`
( 2 )
SAE - LOW oil at 20 0
( b )
Water at 20 0
( C )
Glycerine at 40 0 0
( 51 kPa , Re = 127 , laminar ; 0.5 kPa , Re = 13000 , not laminar ; 153 kPa , Re = 42, laminar )
V = Q/ A = 0. 00.02 1 (* * 0. 01 2 ) = 0. 637 m/s.
= PUB
= uscity
2 ) AD = SHIVL 8 X 0. 1 X 0. 637 * 10_^
- = 51000 Pa . Re = 127 - Laminar
0. 01 -
b ) AD = SHIVL 8 x 1 x 10-3 X 0. 637 X 10`
0. 01 -
- = 510 Pa . Re = 13000 - Not laminar
C ) Ap = SHIVL
_8 ( 0. 3 ) ( 0. 637 ) ( 10 )|
To
( 0. 01 ) 2
~ =| 153 000 Pa| Re = 42 - Laminar
`) No . Flow is not laminar for water at room temperature , a plausible scenario .
Problem 2
Consider flow with discharge Q = 0. 12 L's through an ID 8 mm smooth pipe . Find the flow regime ( laminar
or turbulent ), and the friction factor using the Moody diagram when the a ) fluid is air at 35% C , and b ) fluid is
water at 50%C. Discuss differences .
( 2 : laminar , $= 0.055; 6: turbulent , $ - 0. 023 )
Re - UD
= kinematic
visucity
N
First find the mean velocity ! = = =_ {
a) For air at 35%( with _ _ = 1. 65 x 10^m' /'s we get the Reynolds number R =`_
\You
, which indicates
Laminar flow ( R X 2 x 10'). Hence , 1 = = = 0.055
b ) For water at sorc with `.. = $. 53 x 10^m' I's we get the Reynolds number R =`
_, which
indicates turbulent flow ( 1 5. 3 * 10' for smooth pipes ). From Moody diagram , too two significant
figures, we get / # 0.023....

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- One '18
- Fluid Dynamics, pressure drop, Laminar Flow