Colebrook diagram

Figure 4.2. Colebrook diagram. Figure reproduced from a photocopy from lecture notes by A. Bonazzi [BON 94]...

Using the Colebrook diagram to determine the area-averaged streamwise velocity based on a known head loss is not straightforward. However, by observing that the qnantity ReVl is independent of the velocity, it is possible to rewrite... 

On the Colebrook diagram, different classical flow regimes can be distinguished... 

The smooth turbulent regime corresponds to the lower envelope of the bundle of curves in the Colebrook diagram, for Re> 5 x 10. In the range lO [Pg.81]

The rough turbulent regime corresponds to the conditions under which the linear pressure drop coefficient becomes independent of the Reynolds number (when the latter is sufficiently high). The value of X then depends only on the roughness coefficient that is, the zone to the right of the dashed curve on the Colebrook diagram. 

The Colebrook diagram evaluates the head loss-flow rate relationship for all flow configurations in a straight pipe. This is made possible by the dimensionless representation of the diagram and by the use of the hydrauhc diameter to represent the cross-section of the pipe. It provides a satisfactory estimate in many cases. More accurate and comprehensive evaluations can be found in the book by IdeTcik [IDE 60]. 

The friction factor for laminar flow in pipes Re < 2300) is given by fo = 4/i = For turbulent flow in rough pipes the friction factors depends on both the Reynolds number and the surface roughness of the tube. Colebrook [35] devised an implicit relation for the Darcy friction factor which reproduce the well known Moody diagram quite well. 

The Colebrook equation is convenient for determining the flow rate from the allowable friction loss (e.g., driving force), tube size, and fluid properties. Published plots of/vs. and e/D (i.e., the Moody diagram) are usually generated from the Colebrook equation. 

The familiar Moody Diagram is a log-log plot of the Colebrook correlation on an axis of the friction factor and the Reynolds number, combined with the/ = 64/Re result for laminar flow. 

The friction factor, f, can be found from the Moody diagram (Figure 2.2) which is based on the Colebrook equation in the turbulent regime [7]. 

For turbulent flow, the friction factor is estimated by using the well-known Moody diagram. This can also be calculated by using the Colebrook equation, which is the basis of the Moody diagram [3] ... 

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