# Homework Help: Problem with rectangular and triangular weir

1. Sep 1, 2015

### Queren Suriano

1. The problem statement, all variables and given/known data
A rectangular weir (Cd = 0.623) thin crest without lateral contraction of 1 meter in length and a triangular weir (theta = 90 °) are located on the same channel. If the apex of the triangular weir (Cd = 0.593) is 0.15 meters below the crest of the rectangular weir and neglecting the approach speed determine a) the load on landfills when landings are equal, b) If the discharge of the rectangular weir is greater, determine the load should be for differential flow is maximum

2. Relevant equations
Q( rectangular) =1.84 LH^(3/2)

Q(triangular)= 1.40H^(5/2)

3. The attempt at a solution
a)

Qrectangular = Q triangular
1.84 (1) H1^(3/2) =1.40H2^(5/2). H1: Load rectangular weir, H2: Load triangular weir
H1= H2 -0.15

1.2515(H2)^(5/3) -1.5(H2) =-0.2251
H2=0.21, H2=1.04 m

Is it right??

b) I think I can derivate d(Qrec -Qtriangular) /dH =0
But I dont know if I derivate respect to H1 or H2

Last edited by a moderator: Sep 1, 2015
2. Sep 6, 2015