Flow Over Notches and Weirs A notch is an opening in the side of a tank or reservoir which extends above the surface of the liquid. It is usually a device for. –As it has sharp edges, the flow over the notch is FRICTIONLESS (Ff=0). –these are generally used to measure small discharge across CANAL. WEIR: -These. The bottom edge, over which the liquid flows, is known as sill or crest of the notch and the sheet of liquid flowing over a notch (or a weir) is known as nappe or.

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These are acceptable assumptions for tanks with notches or reservoirs with weirs, but for flows where the velocity approaching the weir is substantial the kinetic energy must be taken into account e. Published by Alessandro Illes Modified over 3 years ago.

Department of the Interior, Bureau of Reclamation.

The wrirs of the “V” should be at least 1. The graph shown is from our fits. The basic principle is that discharge is directly related to the water depth above the crotch bottom of the V; this distance is called head h.

The method of determining the theoretical flow through a notch is the same as that adopted for weirss large orifice. To use this website, you must agree to our Privacy Policyincluding cookie policy.


It is usually a device for measuring discharge. Discharge Head Discharge, Q: Feedback Privacy Policy Feedback.

Flow Over Notches and Weirs

To produce automated calculations, LMNO Engineering used a curve fitting program to obtain the equations which best fit the C and k curves.

Parshall submerged Parshall, Trapezoidal, Rectangular, and U shape.

Occurs if head is being computed and a very low Q is entered e. Head Correction Factor, k: Units in V-notch weir calculation: Standard method for open-channel flow measurement of water with thin-plate weirs. As a result, the discharge through the strip will be. A jet of water from a hose exerts a force on whatever it hits. Consider the two dimensional system in the figure below: This is an initial check of user input.

V Notch Weir Discharge Calculator and Equations

When the length of crest of the weir is same as the width of the channel, the weir is said to be suppressed weir. If you compare it to the graphs shown in the references, it looks nearly identical which implies that our fits are very good. We think you have liked this presentation. V-Notch Triangular Weir Calculator. Water flow measurement in open channels using weirs and venturi flumes – Part 1: Input results in a negative head due to the compiler’s machine precision.

This is a satisfactory assumption for flow over a notch or weir in the side of a large reservoir, but, is the notch or weir is placed at the end of a narrow channel, the velocity of approach to the weir will be substantial and the head h producing flow will be increased by the kinetic energy of the approaching liquid to a value.


About project SlidePlayer Terms of Service. All of the references show similar curves for C and wdirs vs. The notch angle must be between 20 o and o 0. It doesn’t matter how thick the weir is except where water flows over the weir through the “V.

A weir is a notch on a large scale, used, for example, to measure the flow of a river, and may be sharp edged or have a substantial breadth in the direction of flow. To make further flod of this equation we need an expression relating the width of flow across the weir to the depth below the free surface.

For a notch of any shape shown in figure, consider a horizontal strip of width b at a ovre h below the free surface and height d h. The V-notch design causes small changes in discharge to have a large change in depth allowing more accurate head measurement than with a rectangular weir.

A weir is noches notch on a larger scale. Our calculation does not account for partially contracted weirs, but for most practical purposes the difference in C is inconsequential.