Post on 16-Jan-2016
description
Calculation of Normal Depth for Uniform Open Channel Flow
Using the Manning Equation
1. Trapezoidal Channel Calculations:
Inputs Calculations
Bottom width, b = 6 m 6.393 mp
Manning roughness, n = 0.011
Channel bottom slope, S = 0.0003 m/m Iterative (trial & error) Solution:
Side Slope, z = 2
(horiz:vert = z:1)
1 6.218
Volumetric Flow Rate, Q = 15 mc 2 28.596
1.5 14.859
1.1 7.591
1.01 6.348
1.02 6.479
Q*n/(1.49*S1/2) =
A*R2/3 = (3yo + 2yo2)*{(3yo + 2yo
2)/[3 + 2yo(1 + 22)]1/2}2/3
yo ,m (3yo + 2yo2)*{(3yo + 2yo
2)/[3 + 2yo(1 + 22)]1/2}2/3
NOTE: In this example the value of yo, correct to 3 significant figures is 1.01 m
NOTE: For a trapezoidal channel: A*R2/3 = (3yo + 2yo2)*{(3yo + 2yo
2)/[3 + 2yo(1 + 22)]1/2}2/3