I
TM 5820-4/AFM 885, Chap 4
Type of Structure and Design of Entrance
Coefficient K e
U.S. Army Corps of Engineers,
Variables in the equation are defined in appendix
values of n by modifying the culvert length as
D.
directed in paragraph B6, which describes use
of the outlet-control nomography. The value of
Adding the three terms and simplifying, yields for
H must be measured from some "control" ele-
full pipe, outlet control flow the following expres-
vation at the outlet which is dependent on the
sion:
rate of discharge or the elevation of the water
surface of the tailwater. For simplicity, a value
hO is used as the distance in feet from the culvert
invert (flow line) at the outlet to the control el-
evation. The following equation is used to com-
This equation can be solved readily by the use
pute headwater in reference to the inlet invert:
of the full-flow nomography, figures BII through
B17. The equations shown on these nomo-
HW = hO + H LSO . . . . . . . . . . . . . . . . . . . . . . (2)
graphy are the same as equation 1 expressed in
a different form. Each nomograph is drawn for
b. Tailwater elevation at or above the top of the _
a single value of n as noted in the respective
culvert barrel outlet (fig B1OA). The tailwater
figure. These nomography may be used for other
B12
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