How do you calculate rectangular weir?

How do you calculate rectangular weir?

The equation recommended by the Bureau of Reclamation in their Water Measurement Manual, for use with a suppressed rectangular weir is: Q = 3.33 B H3/2, where Q is the water flow rate in ft3/sec, B is the length of the weir (and the channel width) in ft, and H is the head over the weir in ft.

What is a sharp crested weir?

Sharp crested weirs (also called thin-plate weirs or notches) are used to obtain discharge in open channels by solely measuring the water head upstream of the weir. Weirs are extensively used in irrigation practices, laboratories and industry.

How do you calculate water flow in a weir?

Calculation

  1. Q = 0.66 x cB x (2g)0.66 x H1.5
  2. where;
  3. Q = water flow rate, m3/sec.
  4. B = width of the weir, metres*
  5. c = discharge coefficient, average 0.62.
  6. g = gravitational constant, 9.81.
  7. * Note’; if the weir is narrower than the channel feeding it, shorten B by 0.2xH.

What is rectangular weir?

Rectangular weirs and triangular or v-notch weirs are often used in water supply, wastewater and sewage systems. They consist of a sharp edged plate with a rectangular, triangular or v-notch profile for the water flow.

What is contracted rectangular weir?

A contracted weir means that the ditch or canal leading up to the weir is wider than the weir opening itself. The water before the weir should be held in a relatively calm and smooth pool. There should be air (not trapped) underneath the water leaving the weir. The Length is the bottom width of the weir.

How is discharge calculated on a sharp crested weir?

Conclusions: For a suppressed rectangular, sharp-crested weir, equation (8), Q = 3.33BH3/2, may be used if H/P < 0.33 & H/B < 0.33.

What is the difference between sharp crested weir and broad crested weir?

Explanation: The sharp crested weir will help in measuring the discharge of the water from the small rivers and canals and the weir is placed in the direction of the flow of water. The broad crested weir is one which the water flow discharge in measured from large water bodies like big canals.

What is the difference between broad crested weir and sharp crested weir?

Broad-Crested weirs are much thicker in cross section when compared to sharp-crested weirs. They are commonly used to measure the discharge of larger rivers and agriculture / irrigation canals.

Can a sharp crested weir be used as a flow measuring device?

Theory. 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.

What is the CD for a weir?

The weir coefficient, since it is a function of the gravitational constant, is not dimensionless and therefore has different values depending on which unit system you are using. For example, a weir coefficient (C) of 3.00 in English Units would be 1.66 in SI units.

How is weir discharge calculated?

Weirs to Measure Flow It works by raising the water level upstream of the weir, and then forcing the water to spill over. The more water is flowing over the weir, the deeper the water will be upstream of the weir. So measuring flow rate (CFS) can be done by simply measuring the depth of the water upstream.

What is chezy formula used for?

The Chézy formula is an semi-empirical resistance equation which estimates mean flow velocity in open channel conduits.

What is Kutters formula?

Kutter’s formula – Fórmula de Kutter used in Chézy’s formula for calculating the velocity of water in open channels : The most common expression of Kutter’s formula is: C = 100 1 + m R ( h ) {\displaystyle \ C={\frac {100}{1+{\frac {m}{\sqrt {R(h)}}}}}}

Why are sharp crested weirs used?

The V-notch, sharp-crested weir is especially good for measuring low flow rates. The flow area decreases as H increases, so a reasonable head is developed even at a very small flow rate.

How do you calculate discharge using rectangular notch?

The formula for Discharge in Rectangular Notch is – (Where B = width of notch, and H = height of liquid above the sill of the notch)

  1. 3 2 C d L 2 g H 3 / 2.
  2. 3 2 C v L 2 g H 3 / 2.
  3. 3 2 C c L 2 g H 3 / 2.
  4. 2 3 C d L 2 g H 3 / 2.