Unformatted text preview: ly to higher Re, such as large dams on rivers.
The broad-crested weir of Fig. 10.16b is considerably more sensitive to geometric
parameters, including the surface roughness of the crest. If the leading-edge nose is
rounded, R/L 0.05, available data [19, chap. 7] may be correlated as follows: | v v Round-nosed broad-crested weir: Cd | e-Text Main Menu | 0.544 1 */L
H/L Textbook Table of Contents 3/2 (10.57) | Study Guide 10.7 Flow Measurement and Control by Weirs *
L where 0.001 0.2 691 /L The chief effect is due to turbulent boundary-layer displacement-thickness growth *
on the crest as compared to upstream head H. The formula is limited to H/L 0.7,
/L 0.002, and V1H/
3 E5. If the nose is round, there is no significant effect of
weir height Y, at least if H/Y 2.4.
If the broad-crested weir has a sharp leading edge, thus commonly called a rectangular weir, the discharge may depend upon the weir height Y. However, in a certain
range of weir height and length, Cd is nearly constant:
broad-crested weir: Cd 0.462 for H
L 0.22 0...
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- Spring '08
- Fluid Dynamics, Fig, e-Text Main Menu, subcritical flow