FLOW IN PIPES AND CHANNELS 49
25000
20000
Shear stress (N/m
2 )
15000
10000
5000
0 500 1000
Shear rate (s−^1 )
1500 2000 3000
Slope = 6.4 Ns/m^2
Intercept = 1500 N/m^2
Figure 3g.
100,000
10,000
Shear stress (N /m
2 )
1000
10 100 1000
Shear rate (s−^1 )
10,000 100,000
Figure 3h.
(b) a large pump should force the material through the present line, or
(c) a large pump should supply the liquid through a line of twice the cross-sectional
area.
Given that theflow properties of the pur ́ee can be described by the Casson equation:
Ry^1 /^2 DRY^1 /^2 C
(
(^) c
dux
dy
) 1 / 2
whereRYis a yield stress, here 20 N/m^2 , (^) cis a characteristic Casson plastic viscosity,
5Ns/m^2 ,anddux/dyis the velocity gradient, evaluate the relative pressure drops of the
three suggestions, assuming laminarflow throughout.