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Unformatted text preview: s clearly not dimensionally consistent, it requires a conversion factor which changes with the system of units used:  eText Main Menu  Textbook Table of Contents  Study Guide Chapter 10 OpenChannel Flow 1.0 SI units 1.486 BG units (10.17) Recall that we warned about this awkwardness in Example 1.4. You may verify that
is the cube root of the conversion factor between the meter and your chosen length
scale: In BG units,
(3.2808 ft/m)1/3 1.486.*
The Manning formula for uniformflow velocity is thus
V0 (m/s) 1.0
1/2
[Rh (m)]2/3S0
n (10.18) 1.486
1/2
[Rh (ft)]2/3S0
n V0 (ft/s) The channel slope S0 is dimensionless, and n is taken to be the same in both systems.
The volume flow rate simply multiplies this result by the area:
Uniform flow: Q V0A n 2/3 1/2
ARh S0 (10.19) Experimental values of n (and the corresponding roughness height) are listed in Table
10.1 for various channel surfaces. There is a factorof15 variation from a smooth glass
surface (n 0.01) to a treelined floodplain (n 0.15). Due to the irregularity of typical
channel shape...
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This note was uploaded on 10/27/2009 for the course MAE 101a taught by Professor Sakar during the Spring '08 term at UCSD.
 Spring '08
 Sakar

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