Tag Archives: head over a weir

Proportional Sutro Weir Design Calculation Excel Spreadsheet

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Where to get a Proportional Sutro Weir Design Calculation Excel Spreadsheet

For a proportional sutro weir design calculation Excel spreadsheet in either U.S. or S.I. units, click here to visit our spreadsheet store.  Obtain convenient, easy to use spreadsheets for proportional sutro weir design calculations at reasonable prices. Read on for information about the use of a proportional sutro weir design calculation Excel spreadsheet.

Principles of a Proportional Sutro Weir Design Calculation Excel Spreadsheet

For the commonly used rectangular weir or V-notch weir, the flow rate over the weir Diagram for proportional sutro weir design calculation excel spreadsheetincreases as the head over the weir increases, but the flow rate increases at a faster rate than the head over the weir.  For some applications, it is desirable for the flow rate over a weir to be proportional to the head over the weir.  The sutro weir, also known as a proportional weir accomplishes this by having the width of the opening above the weir crest decrease with increasing head over the weir crest as shown in the diagram of a sutro weir at the right.  Equations that can be used for proportional sutro weir design are discussed in the next section.

Equations for Proportional Sutro Weir Design Calculation Excel Spreadsheet

Equations for the base width and base height of a sutro weir are as follows:

base height equation for proportional sutro weir design calculation Excel spreadsheet

base width equation for proportional sutro weir design calculation Excel spreadsheet

  • Wb  =  base width in ft (m for S.I. units)
  • Hb  =  base height in ft (m for S.I. units)
  • Hc  =  max height or curved portion of weir in ft (m for S.I. units)
  • Qmax  =  design maximum flow over the weir in cfs (m3/s for S.I. units)
  • Qmin  =  design minimum flow over the weir in cfs (m3/s for S.I. units)
  • g = acceleration of gravity = 32.17 ft/s/s (9.81 m/s/s for S.I. units)

The equation for the curved portion of a proportional sutro weir is:

Curve Equation for proportional sutro weir design calculation Excel spreadsheet

X and Z are position parameters as shown in the diagram above.  They will have the same units as Wb .

A Screenshot for a Proportional Sutro Weir Design Calculation Excel Spreadsheet

For a proportional sutro weir design calculation Excel spreadsheet with calculations in S.I. or U.S. units, or for other spreadsheets for open channel flow measurement calculations, see: www.engineeringexceltemplates.com

The Excel spreadsheet screenshot below shows part of a spreadsheet for proportional sutro weir design calculations, available  at our spreadsheet store in either U.S. or S.I. units at a very reasonable price.

 Screenshot of Proportional Sutro Weir Design Calculation Excel Spreadsheet

Reference

1, U.S. DOT, Fed Highway Admin, Urban Design Manual, Circular No. 22, 2nd Ed. 2001  (Publ. No. FHWA-NHI-010021-HEC-22)

2. Bengtson, Harlan H., “Proportional Weir Design Equations,” an online blog article

V Notch Weir Calculator Excel Spreadsheet

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Where to Find a V Notch Weir Calculator Excel Spreadsheet

To obtain a V notch weir calculator Excel spreadsheet, click here to visit our spreadsheet store. Why use online calculators or hand calculations when you can buy a V-notch weir calculator excel spreadsheet for only $11.95.  Read on for information about Excel spreadsheets that can be used as v-notch weir open channel flow calculators.

As you can see in the diagrams and picture below, the name, v notch weir, is a good description of the device, simply a v shaped notch in a plate placed in an open channel so that the water is forced to flow through the v notch.  It can be used to measure the open channel flow rate, because the height of water above the point of the v notch can be correlated with flow rate over the weir.  The v-notch weir works well for measuring low flow rates, because the flow area decreases rapidly as the head over the v notch gets small.

Background for Sharp Crested Weirs

Picture for V notch weir calculator excel spreadsheetThe v notch weir is only one of several possible types of sharp crested weirs.  The image at the left shows a picture of a v-notch weir. Acknowledgement of Image Source:              RS Hydro www.rshydro.co.uk                            The diagram below right shows a longitudinal cross-section of a sharp crested weir with several commonly used parameters identified on the diagram.  The weir crest is the term used for the top of the weir.  In the case of a v notch weir, the crest is the point of the v-shaped notch.  The term nappe refers to the sheet of water flowing over the weir.  The equations to bediagram for v notch weir calculator excel spreadsheet  discussed in this article for calculating flow over a v-notch weir require free flow over the weir.  This means that there must be air under the nappe, as shown in the diagram.  The drawdown is the decrease in water level going over the weir caused by the acceleration of the water.  The measurement, H, shown in the diagram is referred to as the head over the weir.  P in the diagram is the height of the weir crest, and the open channel flow rate (also the flow rate over the weir) is shown as Q.

Picture Credit:  U.S. Forest Service

A V Notch Weir Calculator Excel Spreadsheet for a 90 Degree Notch Angle

v notch weir calculator excel spreadsheet diagram

The equation shown below is recommended by the U.S. Dept. of the Interior, Bureau of Reclamation in their Water Measurement Manual (ref #1 below) for calculations with a fully contracted, 90o, v notch, sharp crested weir with free flow conditions and 0.2 ft < H < 1.25 ft.

In U. S. units:  Q = 2.49H2.48, where Q is discharge in cfs and H is head over the weir in ft.

In S.I. units:  Q = 1.36H2.48, where Q is discharge in  m3/s and H is head over the weir in m.

The conditions for the v notch weir to be fully contracted are:

H/P < 0.4,    H/B < 0.2,    P > 1.5 ft (0.45 m),   B > 3 ft (0.9 m)

The diagram above shows the parameters H, P, θ and B for a v notch weir as used for open channel flow rate measurement in a v notch weir calculator excel spreadsheet.

Screenshot of a V Notch Weir Calculator Excel Spreadsheet

The screenshot below shows a v notch weir calculator excel spreadsheet for making 90o, v-notch weir calculations in U.S. units.  Based on specified values for H, P, & S, along with Hmax, the maximum expected head over the weir, the spreadsheet checks on whether the required conditions for fully contracted flow are met and then calculates the flow rate, Q.  This Excel spreadsheet and others for v notch weir calculations are available in either U.S. or S.I. units at a very low cost (only $11.95)  in our spreadsheet store.

References:

1. U.S. Dept. of the Interior, Bureau of Reclamation, 2001 revised, 1997 third edition, Water Measurement Manual, available for online use or download at: http://www.usbr.gov/pmts/hydraulics_lab/pubs/wmm/index.htm.

2. Bengtson, Harlan H., Open Channel Flow III – Sharp Crested Weirs, an online continuing education course for PDH credit, http://www.online-pdh.com/engcourses/course/view.php?id=87

3. Munson, B. R., Young, D. F., & Okiishi, T. H., Fundamentals of Fluid Mechanics, 4th Ed., New York: John Wiley and Sons, Inc, 2002.