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An end contraction is when the length of the weir (L) is less than the width of the Channel and a nappe contracts either one or both sides of the weir.
- What is the effect of end contraction on the discharge through a weir?
- What is a sharp crested weir?
- What is the reduction in the crest length due to each end contraction?
- What happens when the water flows approaching a weir?
- What is meant by end contraction?
- What is ogee weir?
- What is a contracted weir?
- What is the difference between broad crested weir and sharp crested weir?
- What is the weir equation?
- What is the purpose of a broad crested weir?
- What are weirs quizlet?
- How do you escape a weir?
- What is velocity of approach in weir?
- What is the theoretical value of the coefficient of contraction for the sharp edge orifice?
- Is contraction least at Vena Contracta?
What is the effect of end contraction on the discharge through a weir?
Based on how the expression is used there, I gather that it really refers to the reduction in width of the sheet of water flowing over the weir. That is, the ends contract inward (because there is a flow inwards along the walls across the flow leading in to the weir). describes the effect on pages 3 and 4.
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 is the reduction in the crest length due to each end contraction?
What is the reduction in crest length due to each end contraction? Explanation: Francis through his experiment had derived this empirical relation. Explanation: In Francis formula, the effective length is L-0.2H.
What happens when the water flows approaching a weir?
As the liquid approaches the weir, the liquid level gradually drops and the flow velocity increases. Downstream from the weir, a jet is formed. This is called the nappe and it is ventilated underneath to enable it to spring free from the weir crest [Barna (1969)].
What is meant by end contraction?
If the weir width is less than the width of the channel, it is known as weir with end contractions. The end contraction results into the decrease of the width of neppe. ... The approximate value of end contraction is 0.1 H, where H, is height over the weir crest.
What is ogee weir?
An ogee crest weir is a common weir type whose cross-sectional profile corresponds to the shape of the underside of a sharp-crested weir nappe. Just as the shape or trajectory of the sharp-crested weir nappe changes with flow rate, so does the ogee crest profile.
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.
What is the difference between broad crested weir and sharp crested weir?
The thin plate (or sharp-crested) weir is usually used to measure watersheds, creeks, and small streams. ... 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.
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 the purpose of a broad crested weir?
The broad crested weirs are a hydraulic structures widely used for depth control and flow measurement in field and laboratory canals . The geometry described as a flat-crested structure with a length (L) of crest large enough compared to the flow thickness over the crest of the weir.
What are weirs quizlet?
Weirs. elevated structures in open channels that are used to measure flow and control outflow from basins and drainage channels.
How do you escape a weir?
Water falls over the weir, drives to the bottom of the riverbed, bounces back up and then rejoins the downward flow at the top. These circulating stoppers can be aggressive and impossible to escape. You can try to swim down or sideways to and exit the circuit, and then rise to the surface.
What is velocity of approach in weir?
i. The average velocity of water in a channel at the point where the depth over a flow measuring weir is recorded.
What is the theoretical value of the coefficient of contraction for the sharp edge orifice?
for sharp edged orifices the value of Cv is 0.98.
Is contraction least at Vena Contracta?
Vena contracta is the point in a fluid stream where the diameter of the stream is the least, and fluid velocity is at its maximum, such as in the case of a stream issuing out of a nozzle (orifice). ... The effect is also observed in flow from a tank into a pipe, or a sudden contraction in pipe diameter.
