Function

The Advanced Weir Design uses the methodology described in HEC-22 Manual. The weir flow is determined as:

Q = Cw L H 0.5   for the Rectangular Weir without Contracted End
Q = Cw (L - 0.2 H) 0.5   for the Rectangular Weir with Contracted End

where:    Q = discharge, ft3/s (m3/s)
Cw = weir coefficient, 3.33 in English units (1.84 in Metric units)
L = weir length, ft (m)
H = head above weir crest, ft (m)

Q = Cw [L + 0.8 H tan(Ø/2)] 1.5   for Trapezoidal Weir

where:    Q = discharge, ft3/s (m3/s)
Cw = weir coefficient, 3.33 in English units (1.84 in Metric units)
L = weir length, ft (m)
Ø = internal angle of the two sides, degrees
H = head above weir crest, ft (m)

Q = Cw tan(Ø/2) H 2.5   for V-Notched Weir

where:    Q = discharge, ft3/s (m3/s)
Cw = weir coefficient, 2.5 in English units (1.38 in Metric units)
Ø = angle of v-notch, degrees
H = head above weir crest, ft (m)

This command designs a weir structure and calculates its stage-discharge curve. Select Weir Design from the Structure menu in the Hydrology Module to display the design dialog. Select the Type of the weir , Rectangular, Trapezoidal or V-notched. Enter the dimension for the weir. In the Invert Elev box, type the absolute elevation at which the weir will be attached to a reservoir. The attachment point is at the bottom of the weir. In the Coefficient box, type a weir coefficient value. In the Number of Openings box, enter the number of weirs you want to combine.

In the Headwater box, type the absolute headwater surface elevation.Click on the Calculate button, the maximum discharge and flow velocity through the weir would be computed and displayed.

Click on the Stage-Discharge Result button to display the stage-discharge curve in the Stage-Discharge Result Dialog. This dialog allows you to write the stage-discharge data to a stage-discharge file(.STG), and draw the stage-discharge curve on the screen. From the Stage-Discharge Curve Draw Settings dialog , you can specify how to draw the curve.

 Advanced Weir Design Dialog Stage-Discharge Limits Dialog Stage-Discharge Result Dialog

Prompts

Advanced Weir Design dialog: Fill in values.