FLOOD02273

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Basin: Statewide
• Title: Hydraulic Design of Energy Dissipators for Culverts and Channels
• Date: 12/1/1975
• Prepared For: USDOT
• Prepared By: Federal Highway Administration
• Floodplain - Doc Type: Educational/Technical/Reference Information

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Wingwall flare Sw = 450 with lO foot apron

Find: Flow condition at end of apron - Y and v.

solution:

l. Find outlet velocity from figure III-9 with

Q/BD3/2=4.83 and TW/D~O
Yo/D =0.68
Yo=0.68(5)=3.40
Vo=d/A=270/3.4(5)=l5.88 fps

2. Find outlet Froude number

Fr = Vo/lgyo = l5.88/ll09.48' = l.52

3. Find S

tanS = l/3Fr = l/3(l.52) = 0.22
S = l2.37

4.

Apron Length/Diameter = lO/5 =, 2
Use figure IV-A-4 for average depth, YA'

YA = 0.26(3.4) = 0.88 feet

5.

From figure IV-A-2 the average velocity VA is:

VAlVo = 1. 2
VA = l5.88(1.2)
VA = V2 = 19.1 fps

6. Sw>S use Sw

W2 = Wo + 2L tan (SW)
W2 = 5 + 2(lO) (1.0) = 25 feet

7.

Sw was used:

Y2 = YA = 0.88 feet
W2 = Q/VAYA = 270/(l9.l)0.88
W2 = 16.1 ft.< 25 ft.

Alternate Solutions Using Energy Equation

(l) Assume W2 = full width between wingwalls at the
end of the apron

W2 = Wo + 2L tan 450 = 25 feet
A2 = W2Y2 = 25 Y2, V2 = Q/A2 = 270/25Y2 = lO.8/Y2

IV-A-5