How do you size a weir?
There should be air (not trapped) underneath the water leaving the weir. The Length is the bottom width of the weir. The height is measured from the bottom of the weir opening to the top of the water level ponded behind the weir (not the water level right as it leaves the weir).
What is weir coefficient?
The weir coefficient (as shown above in the weir equation) is a lumped parameter that includes the discharge coefficient, the gravitational constant, and constants based on geometric properties.
How do you calculate flow through a weir?
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. Use of this equation is subject to the condition that H/P < 0.33 and H/B < 0.33.
What is crest length of weir?
A broad-crested weir has crest length of Lb = 0.75 m, crest width of Lw = 1.0 m, and crest height of p = 0.30 m. The water surface at the approach section is 0.20 m above the crest, that is h0 = 0.20 m.
What is the height of weir?
The height of the weir from the bottom of the channel to the crest should be at least 2 times the maximum expected head of liquid above the crest. This is necessary to lower the velocity of approach. The weir height should never be less than 1 foot (0.3 m).
What is the breadth of a weir?
The weir breadth is the same as the channel width. The weir surfaces are of planed wood or smooth concrete. The downstream nappe is fully aerated, and the weir entrance is square. The profile for the second weir form is shown in figure 26.
What are the various factors governing the design of weirs?
Conditions for Stability of Weirs
- There must be no tension in the masonry or in the contact plane between weir and the foundation.
- There must be no overturning.
- There must be no tendency to slide on the joint with the foundation or any horizontal plane above the base.
What is effective head on weir?
Rectangular Weir Equation The sum b+Kb is called “effective width” and the sum h+Kh is called “effective head.” The value for g is 9.8066 m/s2 and Kh=0.001 m.
What is Francis formula?
According to Francis formula, the discharge over a rectangular weir is (where n = Number of end contractions) A. ( 2/3) × Cd (L – nH) × √(2gh)
What is head in weir?
The head is the height of water above the blade edge or the bottom of a Vnotch, measured at a point where the velocity head (or approach velocity) is negligible (figure 56). In practice, this point is located four to six times the measuring head upstream from the center of the weir blade.
What is design loading rate?
You can calculate loading rates with a few basic steps. Calculate the hydraulic loading rate with the formula: Hydraulic loading rate = Design flow (gal/day) / Area (feet ^2). Design flow is the volume of waste water per day.
What is BOD loading rate?
Organic loading rate is defined as the application of soluble and particulate organic matter. It is typically expressed on an area basis as pounds of BOD5 per unit area per unit time, such as pounds of BOD5 per square foot per day (lb/ft2/day).
How do you calculate V notch?
V Notch Weir Equation for Notch Angle Other than 90 Degrees That equation is: Q = 4.28 Ce Tan(θ/2)(H + k)5/2, where Q and H are as previously defined, θ is the angle of the v notch, Ce is the effective discharge coefficient, and k is a head correction factor.
What is orifice coefficient?
The coefficient of discharge for orifices in pipes varies from 0.60 to 0.80 and varies with the diameter ratio. For flow nozzles in pipelines, the coefficient varies from 0.96 to 1.2 for turbulent flow and varies with the diameter ratio.
Is code for design of weir?
The other four stan- dards already published are IS : 6966-1973*, IS : 7349-1974t, IS : 7720-1975# and IS : 8408-19768. *Criteria for hydraulic design of barrages and weirs. *Code of practice for operation and maintenance of barrages and weirs.
How many factors govern the design a weir or a barrage?
Factors Affecting Design of a Barrage | Flood Data, Barrage Width, Afflux, Crest.
Why should the weir have a sharp crest?
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.
What is Bazin formula?
An equation for calculating the average velocity of water flowing in an open channel, proposed in 1897 by H. E. Bazin (1829–1917). It relates the Chezy discharge coefficient (C) to the hydraulic radius (r) and a channel roughness coefficient (k1) by the formula: C = 157.6/[1 + (k1/r1/2)].
What is a weir overflow?
A weir is an overflow structure that is used to alter flow characteristics. In the example below, the water is flowing from left to right. The black triangular-shaped structure is the weir. It is impeding the flow of water causing the water to flow over the weir structure.