Page 167 - Mechanical Engineer's Data Handbook

156 MECHANICAL ENGINEER'S DATA HANDBOOK

Kinematic viscosity in a circular pipe is parabolic, being a maximum at the
pipe centre.
Dynamic viscosity
Kinematic viscosity =
Density
or v=- P
P

Dimensions of viscosity

Dynamic viscosity: ML- ' T-
Kinematic viscosity: L2 T- '

Units with conversions from Imperial and other units

Dynamic viscosity Kinematic viscosity
SI unit: Nsm-2 SI unit: m2 s- '
llbf-s ft -' =47.9 N s m-' 1 ftz s- ' =Om29 mz s- '
1 lbf-hft-2 = 17.24 N s m-2 1 ft2 h- ' = 334 mz s- '
Velocity distribution
1 poundal-s ft - =
1.49 N s m-2
llbft-' s-' =
1.49 kg ms - '
1 slugft-'s-'= Flow Q=?c (Pi -p2)r4
47.9 kgms-' 8PL

Mean velocity V= (Pi -P2)rZ
Viscosity of water 8PL
Maximum velocity V, =2V
Approximate values at room temperature:
p=10-3Nsm-z 4.4.3 Laminar flow between flat plates
y = 10-6mZs-l

(PI -p2W
Flow Q=
Temperature Dynamic viscosity 12pL
("C) (x 10-3Nsm-i)
Mean velocity V= (Pi -Pz)t2
0.01 1.755 12pL
20 1.002 Maximum velocity V,=$ V
40 0.65 1
60 0.462
80 0.350
100 0.278

4.4.2 Laminar flow in circular pipes
The flow is directly proportional to the pressure drop
for any shape of pipe or duct. The velocity distribution