The Vnotch weir
Today we are going to demonstrate the Vnotch weir. ...
The width of the flume is 6 inches, or 0.5 ft. [Point to the channel width]. ... We turn on the pump. .... We set the bed slope equal to 1% and check the level [Point to the level]. ... We set the point gage at zero at the weir crotch [Point to the gage].
... Now we are going to measure the hydraulic head H over the weir. ... The head measurement should be taken at a distance L of at least 4 times the hydraulic head H. ... We try a distance of 150 mm. ... The measured hydraulic head is H = X mm, which is less than 1/4 of 150 mm. ... In U.S. Customary units, the hydraulic head is H = Y ft. ... The ratio of head to width H/B is equal to Y/0.5 = YYY, which is less than 0.2. ... Therefore, the weir is operating under fully contracted conditions.
The discharge through the Vnotch weir is:
The discharge coefficient C_{e} is a function of the angle θ of the weir. ... In this case, for θ = 90°, the discharge coefficient C_{e} is 0.578. ... The head correction k is also a function of the angle θ of the weir [Point to the angle of the weir]. ... In this case, for θ = 90°, the head correction k is 0.0029.
Therefore, the discharge is YY cfs.
The calculation can be performed using the online calculator http://ponce.sdsu.edu/onlineveenotch.php
