2.0

Calculating Weir Values
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8 In the Height box, type a height for the weir.
The computed values for the weir display at the bottom left of the dialog box.
The box at the top right area of the dialog box displays a graphic of the
currently defined weir. This information is for display only and cannot be
edited.
NOTE
If the data you entered has an error, the weir graphic image does not
display. Check for an error message at the bottom of the dialog box.
9 Click OK to exit the dialog box.
Rectangular Weir Formulas
You can use the Rectangular Weir Calculator to calculate hydraulic values for
suppressed and contracted rectangular weirs.
The following formula is used to calculate the design flow rate for a suppressed
weir.
QcLgH
2
3
15
2( )
.
The following formula is used to calculate the design flow rate for a contracted
weir, including a correction (-0.2H) to the effective length to account for edge
contractions.
QcL HgH 
2
3
15
02 2(.)()
.
where:
Q = Design flow rate
c = Weir coefficient
L = Length of weir
g = Acceleration due to gravity (32.174 ft/s
2
or 9.807 m/s
2
)
H = Weir head
Specifying a Rectangular Weir Coefficient
The Rectangular Weir Coefficient dialog box displays descriptions of weir
structures and the associated velocity coefficients.
To select a coefficient from the dialog box
1 In the Rectangular Weir Calculator dialog box, click the Select button next to
the Coefficient text box to display the Rectangular Weir Coefficient dialog box.
2 Select a coefficient by placing your cursor in the appropriate column and
clicking anywhere in the text box that contains the value you want to use.
Use the navigation buttons on the right side of the dialog box to move through
the list of descriptions and coefficients.
You can add a new coefficient:
n
Click Insert to add a new row above the row you currently have selected.
n
To add data, select an empty text box, and type the new description and
coefficient.
3 Click OK to return to the Rectangular Weir Calculator dialog box.