- #1
ShawnCohen
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Homework Statement
A 4m wide channel has a bed slope of 1 in 1500 and a Manning's roughness coef n=0.01. A broad crested measuring weir in the form of a streamlined hump 0.4m high spans across the full width of the channel. the discharge is 10.5m^3/s. Determine
i)the uniform depth of flow
iv)the depth of water on the weir, is this critial
Homework Equations
Mannings equation: Q=A^(5/3)*(S)^(1/2)/(n*P^(2/3)) where A is cross sectional area, S is bed slope, P is wetted perimeter
Bernoulli equation elevation+(v^2)/(2*g)=constant (i ignore pressure head here as I am working on surface so use atmospheric pressure as zero)
Specific energy - E=d+(Q/w)^2/(2*g*d^2) where d is the depth and w is the width
The Attempt at a Solution
i use mannings equation to determine the depth and i get 1.22m, but then when i try and find the depth on top of weir i get nowhere, in face if i work out the minimum possible specific energy i get 1.333 and on top of the weir i get 1.05, so I am clearly going wrong somewhere. any help anyone??