Open Channel Flow (mannings equation)

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SUMMARY

The discussion centers on calculating the bottom width of a trapezoidal channel using Manning's equation. Given a Manning's n value of 0.025, a bed slope of 0.0045 m/m, and a discharge of 7.5 m³/s, the user seeks assistance in applying the formula. The relevant equation is V = (1/n) * R^(2/3) * S^(1/2), where the user is unsure about utilizing graphs for solutions. A recommended resource is the Manning's calculator available at flowsizer.com for streamlined calculations.

PREREQUISITES
  • Understanding of Manning's equation and its components
  • Familiarity with trapezoidal channel geometry
  • Basic knowledge of hydraulic principles and flow calculations
  • Ability to interpret and utilize hydraulic graphs
NEXT STEPS
  • Explore the use of Manning's equation in various channel shapes
  • Learn how to calculate hydraulic radius (R) for different channel geometries
  • Investigate the impact of varying Manning's n values on flow rates
  • Utilize online calculators like flowsizer.com for practical applications of Manning's equation
USEFUL FOR

Civil engineers, hydraulic engineers, and students studying fluid mechanics will benefit from this discussion, particularly those involved in channel design and flow analysis.

Stacyg
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A trapezoidal channel with side batters 1:1 and Manning's n value of 0.025 has a bed slope of 0.0045 m/m. When the depth is equal to the bottom width the discharge is 7.5 m^3/s. Calculate the bottom width to the nearest 0.01m.

Using mannings equation

V= 1/n.R^2/3.S^1/2

S=0.0045 n=0.025 Q=7.5

Q=V.A V=Q/A

I don't know where to start I know how to use the equation and we have been shown how to use some graphs for the solution of mannings formula but I'm not sure on using them.
Any help would be great thanks
 
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Hey,

I guess you may have found the answers you are looking for. But just in case you are still searching go to http://flowsizer.com" they have a nice clean mannings calculator that will get you the answers to those equations
 
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