# How is weir discharge calculated?

## How is weir discharge calculated?

The Equation

1. The Equation used to determine the flow rate of a Rectangular Contracted Weir is:
2. = Flow Rate in cfs.
3. = Bottom width of the weir in feet.
4. = Height of the upstream water above the weir crest in feet.

### Why is discharge measured near weirs?

Weirs and flumes make excellent flow-measuring devices because they have a one-to-one relationship between discharge and stage. A weir is an overflow structure placed across the flow. If the overflow from the weir is unobstructed by the water level downstream from the weir, a free overfall is said to exist.

#### What is standard weir?

Weirs are structures consisting of an obstruction such as a dam or bulkhead placed across the open channel with a specially shaped opening or notch. Common weir constructions are the rectangular weir, the triangular or v-notch weir, and the broad-crested weir.

What is flow over a weir?

The depth of water above the base of a weir is related to the flow rate through it; therefore, the weir can be used as a flow measuring device. The relationships of flow over weirs can be obtained by applying the energy equation from a point well upstream of the weir to a point just above the weir crest.

What are the causes of failure of weir on a permeable foundation?

The weir failure may take place due to the following reasons

• Piping or undermining.
• By uplift pressure.
• By suction due to standing wave.
• By scour on the U/S and D/S of the weir.

## How do you survive a weir?

You can try to swim down or sideways to and exit the circuit, and then rise to the surface. Higher river flow increases the chances of a stopper in a location. Be aware they can appear at ‘safe’ locations – if locals are safely playing at the base of a weir it might be safe to join in, but never assume this.

### How to calculate the discharge of a rectangular weir?

ISO (1980), ASTM (1993), and USBR (1993) all recommend using the Kindsvater-Carter method for all rectangular weirs. The sum b+K b is called “effective width” and the sum h+K h is called “effective head.” The value for g is 9.8066 m/s 2 and K h =0.001 m. C e is a function of b/B and h/P, and K b is a function of b/B.

#### What are the discharge tables for thin plate weirs?

The discharge tables here are for thin-plate Weirs in general. Before relying on the full flow rates indicated on the tables below, compare the depths indicated in the tables versus your application.

How is the discharge of a weir related to the head?

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 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. Triangular Weir (V-Notch Weir) Equations

How to calculate the height of a weir?

Problem A weir of 8m long is to be built across a rectangular channel to discharge a flow of 9m3/s. If the maximum depth of water on the upstream side of weir is to be 2m, what should be the height of the weir ? Adopt Cd= 0.62. Workings Given, L = 8 m Q = 9 m3/s Depth of water = 2m Cd= 0.62 Let, H = Height of water above the sill of the weir.

12/07/2019