What is a sharp crested weir?

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.

What are sharp crested weirs used for?

The thin plate (or sharp-crested) weir is usually used to measure watersheds, creeks, and small streams. They have also found a use in measuring industrial effluents in the form of weir plates, boxes, and channels. Broad-Crested weirs are much thicker in cross section when compared to sharp-crested weirs.

What is the difference between broad crested weir and sharp crested 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. Weirs are called sharp-crested if their crests are constructed of thin metal plates, and broad-crested if they are made of wide timber or concrete.

What are the different types of weir?


  • Sharp crested weir.
  • Broad crested weir (or broad-crested weir)
  • Crump weir (named after the designer)
  • Needle dam.
  • Proportional weir.
  • Combination weir.
  • MF weir.
  • V-notch weir.

What is the weir equation?

The Weir formula is a formula used in indirect calorimetry, relating metabolic rate to oxygen consumption and carbon dioxide production. According to original source, it says: Metabolic rate (kcal per day) = 1440 (3.94 VO2 + 1.11 VCO2)

What is a contracted 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 discharge is measured in weir?

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 the main difference between a dam and weir?

The only main difference between dam and weir is that dam can store water comparatively for longer duration than weir and the dam is at more height than the weir. 7.

On what basis are the sharp crested weirs classified?

Weirs are commonly named by the shape of their blade overflow opening shape (figure 7-1) for sharp-crested weirs or the flow control section shape for broad-crested weirs. Thus, weirs are partially classified as rectangular, trapezoidal, triangular, etc.

On what basis are the sharp-crested weirs classified?

What is standard weir?

Standard Contracted Rectangular Weirs. The fully contracted rectangular weir (figure 7-1) is the most frequent standard weir used in irrigation. To be fully contracted, all overflow plate sides and ends must be located at least a distance of 2h1max (two maximum measurement heads) from the approach flow boundaries.

What is a sharp-crested weir?

sharp-crested weir consists of a vertical flat plate with a sharp edge at the top (the crest), placed in an open channel so that the liquid must flow over the crest in order to drop into the pool below the weir. Figure 1 below shows a longitudinal section representing flow over a sharp-crested weir.

Which weirs are not sharp crested weirs?

All other weirs are classed as weirs not sharp crested. Sharp-crested weirs are classified according to the shape of the weir opening, such as rectangular weirs, triangular or V-notch weirs, trapezoidal weirs, and parabolic weirs.

Why is the crest of a weir plate sharp?

The crest of the weir is very sharp such that the water will springs clear of the crest. The weir plate is bevelled at the crest edges to obtain necessary thickness.

What is Weir in hydraulics?

Posted in Hydraulics | Email This Post |. Weir is defined as a barrier over which the water flows in an open channel. The edge or surface over which the water flows is called the crest.