Calculation of Flow Rate Over a V Notch Weir

Inputs Calculations

Height of V notch above 1.04

channel invert, P = 2.6 ft

yes

Distance from channel

wall to V notch edge at 1.04

top of overflow, S = 2.6 ft

yes

Max. head expected

1.25 ft yes

Measured head over If all three answers are yes:

the weir, H = 0.62 ft 1.3090

75 degrees Eff. Dischg. Coeff, Ce = 0.576

Head corr. factor, k = 0.0031

Flow Rate, Q = 0.580 cfs

(Fully-Contracted with Notch Angle = q)

P/(2Hmax) =

P/(2Hmax) > 1 ?

S/(2Hmax) =

S/(2Hmax) > 1 ?

over weir, Hmax = 0.2 ft < H < 1.25 ft ?

q in radians =

Notch Angle, q =

[ Ce = 0.607165052 - (0.000874466963)θ + (6.10393334 x 10-6)θ2 ]

[ k = 0.0144902648 - (0.00033955535)θ + (3.29819003 x 10-6)θ2 - (1.06215442 x 10-8)θ3 ]

[ Q = 4.28 Ce Tan(θ/2)(H + k)5/2 ]

NOTE: q is in degrees, not radians in the first two equations.

14

15 30 cfsroughness, n =

Discharge, Q =

0.0000roughness, n =