Page 509 - Air and Gas Drilling Manual

10-34 Air and Gas Drilling Manual
From Equation 9-7, the kinematic viscosity of the foam as it exits this cased
annulus section and starts into the Tee is
0 00009635
.
sfa1
.
0 0690
2
ft
0 00136
.
sfa1
sec
The average velocity of the foam as it exits this cased annulus section and starts
into the Tee is
P at T av1
Q g Q w
P Tee T at
V sfa1
D 1 2 D 2 2
4
,
.
1 826 6 . 537 66
.
( 27 64) 0 234
.
.
4 604 4 . 519 67
,
V
sfa1
.
0 668 2 0 375 2
.
4
V sfa1 30 8 ft/sec
.
Using Equation 6-89 the Reynolds number of the foam as it exits this cased
annulus section and starts into the Tee is
V sfa1 D 1 D 2
N
Rsfa1
sfa1
(30 . ) ( .668 . 0 375 )
8
0
N Rsfa1
. 0 00136
,
N Rsfa1 6 652
The Reynolds number calculation above is greater than 4,000. This indicates that
the flow condition is turbulent. Therefore, the empirical von Karman equation (i.e.,
Equation 6-92) must be used to determine the Fanning friction factor for the foam
flow in this annulus section.
Both annulus section surfaces are commercial steel with the surface roughness