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Unformatted text preview: le 5.7, we could change the scaling variables to ( , , d) and thus arrive at dimensionless head loss versus dimensionless velocity. The result is4
L2 where f Re2
2 (6.65) 1.75
Example 5.7 did this and offered the simple correlation
0.155 Red , which is valid
for turbulent flow with smooth walls and Red 1 E5.
A formula valid for all turbulent pipe flows is found by simply rewriting the Colebrook interpolation, Eq. (6.64), in the form of Eq. (6.65): (8 )1/2 log Red /d
L2 1.775 (6.66) Given , we compute Red (and hence velocity) directly. Let us illustrate these two approaches with the following example.
950 kg/m3 and
2 E-5 m2/s, flows through a 30-cm-diameter pipe 100 m long with
a head loss of 8 m. The roughness ratio is /d 0.0002. Find the average velocity and flow rate. Direct Solution
First calculate the dimensionless head-loss parameter:
4 | v v The parameter | (9.81 m/s2)(0.3 m)3(8.0 m)
(100 m)(2 E-5 m2/s)2 5.30 E7 was suggested by H. Rouse in 1942. e-Text Main Menu | Textbook Table of Contents | Study G...
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- Spring '08