Erosion and Sediment Pollution Control Program Manual.pdf

2. Determine Discharge Velocity (VO) using Figures F.5 and F.6 or by the equation:
V = Q/A
Where: A = Cross-sectional area of the flow (not the pipe)
3. Calculate the Froude Number (Fr) using the equation:
Fr = VO / (32.2 YO)
4. Select a Dissipater Configuration from Figure F.7 that fits the geometry of the outlet.
a) Choose an Expansion ratio (WD/WO) and determine W1/WO
b) Pick the Number of Rows (N r), and Number of Elements (N)
c) Pick h/yA and L/h
5. Determine the Approach Velocity VA, using Figure F.8 for rectangular culverts or Figure
F.9 for circular culverts.
6. Determine Average Depth of Flow (YA) in expansion part of dissipater, using Figure
F.10 for rectangular culverts or Figure F.11 for circular culverts.
7. Determine Dissipater Dimensions and Flow Parameters:
a) Element Height (h)
b) Length between Rows (L)
c) Dissipater Width (WD)
d) Element Width (W1) = Spacing between elements in rows
e) Divergence (ue)
f) Dissipater Drag (CD)
ue = 4/7 + 10L/7WO
g) Element Frontal Area (AF) = W1 h
h) Momentum Correction Coefficient (CP) = 0.7
i) Length of Dissipater (LD)
LD = 2WO + LNr
0. 5
363-2134-008 / March 31, 2012 / Page 413