ME 493 Design Problem 04-11-2015
(Open Channel Flow Hydraulicsl
An open concrete rectangular channel (n=0.013) has three reaches, the following parameters are known for
each of its reaches starting from the upstream (U/S) side to the downstream (D/S) side:
Reach 1. L=1460 ft, section – 56’wx10’H, s=0.0020, yn=7.00′ (normal depth of flow)
Find: The discharge in the channel to the nearest cfs, e=? – What is the critical depth, y.=?
(A 120 ft transition connects reach 1 to reach 2)
Reach 2. L=800 ft, section – 45’Wx11’H, s=0.0020, same e as determined for reach 1
Find: Normal depth of the flow, yn=? (Trial & Error) – What is the critical depth, y.=7
(A 120 ft transition connects reach 2 to reach 3 and there is a Grade Break at the D/S end of this transition)
Reach 3. L=4500 ft, section – 64’wx11’H, 5=0.0010, yn=8.55′ (normal depth of flow)
Find: The discharge in the channel to the nearest cfs, e=7 – What is the critical depth, y.=7
What is the junction discharge (Q at the transition?
(Reach 3 terminates at a free fall)
The channel at the free fal! has a Station of 10+00 and an Elevation (invert) of 1500.00
a) Calculate the Stations & Elevations for all of the U/S reaches including the transitions.
b) Draw a Plan & Profile view for this channel on an 11″x17″ sheet from STA. 10+00 to STA. calcutated in part a,
show the bottom & the top of the channel. Show all calculated stations & elevations on the profile view, show
the critical and normal depths for each reach, label the latter as the Hydraulic Grade Line abbreviated as H.G.L.
Use a horizontal scale of 1″=500’& a vertical scale of 1″=5’for the profile view & a scale of 1″=5(Xt’ in the
teft/right direction & 1″=50′ in the up/down direction for the plan view.
c) Show in the profile view a 5′ diameter junctioning Reinforced Concrete Pipe (RCP) in the middle of the 2nd
transition from U/S, center the RCp vertically as well.
d) Show the RCP in the plan view as wellwith a 9O’junctioning angle.
e) Determine the type & length of the curve for the varied flow at Reach 3 which terminates at a free fall using the
numerical method analysis. Show the results in a manually generated tabutated format.
0 On the plan view of the channel – Show the beginning and ending stations only, the length of each reach and the
size ofthe channel section for each reach.
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