Open Channel Flow (mannings equation) rectangular section

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SUMMARY

The discussion focuses on calculating the depth of flow in a rectangular concrete-lined channel using Manning's equation. The channel has a width of 2 meters, a Manning's n value of 0.012, and a bed slope of 0.0025 m/m, with a discharge of 9 m³/s. To find the depth of flow, participants suggest using the relationship Q = V * A, where the area A can be expressed as A = b * h, allowing for the elimination of velocity (V) to solve for the depth (h).

PREREQUISITES
  • Manning's equation for open channel flow
  • Understanding of hydraulic geometry
  • Basic algebra for solving equations
  • Knowledge of rectangular channel characteristics
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  • Explore the effects of channel slope on flow depth and velocity
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Civil engineers, hydrologists, and students studying fluid mechanics or open channel flow design will benefit from this discussion.

Stacyg
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A rectangular concrete-lined channel is 2m wide with Manning's n 0.012 and a bed slope of 0.0025 m/m. Obtain the depth of flow when the discharge is 9m^3/s.

Q=V.A I have the discharge but how do I calculate the velocity without the area ?? Once I have the velocity I should be able to work it out.

Thanks
 
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You've got two equations with two unknowns: eliminate v. Write the area A as b*h with b the width and h the height of the rectangular cross-section. Now solve for h.
 
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