Advanced Weir Design

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

Q = C_w L H^1.5 for the Rectangular Weir without Contracted End
Q = C_w (L - 0.2 H)^1.5 for the Rectangular Weir with Contracted End

where:    Q = discharge, ft³/s (m³/s)
              C_w = 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 = C_w [tan(Ø/2) H^2.5 + 5/4 L H^1.5 ]for Trapezoidal Weir

where:    Q = discharge, ft³/s (m³/s)
              C_w = 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 = C_w tan(Ø/2) H^2.5 for V-Notched Weir

where:    Q = discharge, ft³/s (m³/s)
              C_w = 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)


Rectangular Weir with Contracted End	Rectangular Weir without Contracted End


Trapezoidal Weir	V-Notched Weir

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.

The program performs two-way calculation: calculate Discharge from Headwater, and calculate Headwater from Discharge. In the Headwater and Tailwater boxes, type the absolute headwater surface elevation and tailwater surface elevation respectively, and the maximum discharge and flow velocity through the orifice would be computed automatically. When Discharge value is entered, the Headwater elevation would be calculated automatically.

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 draw the curve into the drawing or write a .stg stage-discharge file.

The Report Setup chooses between the Standard Report and the PDF Report. The Standard Report is a simple text report of the parameters and results. The PDF Report adds some text formmating and options to draw a schematic of the weir and draw a stage-discharge graph. The Report button generates the weir design report.

The Draw button creates a schematic of the weir with dimensions in the drawing.

The Load and Save buttons store and recall the parameters to a .weir file.



Advanced Weir Design Dialog


Stage-Discharge Limits Dialog


Stage-Discharge Result Dialog


Weir Design Report

Pulldown Menu Location: Structure > Advanced Weir Design
Keyboard Command: weir
Prerequisite: None

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