Question

For a saddle siphon, the maximum operative head is 4.53 m. The width and height of the throat of the siphon are 5 m and 2.25 m respectively. The coefficient of discharge is 0.90. How many units are required to pass a flood of 350 cumecs? (Assume g = 10 m/s^2)

(a) One

(b) Two

(c) Three

(d) Four

I have been asked this question at a job interview.

My question comes from Shaft Spillway topic in chapter Spillways, Energy Dissipators and Spillway Gates of Irrigation Engineering

Answer 1

The correct option is (d) Four

To explain I would say: The discharge through the siphon is given by the equation:

Q = Cd. A. (2gH)^1/2 Where Cd = 0.9, H = 4.53 m and A = 5 x 2.25 = 11.25 m^2

Q = 0.9 x 11.25 x (2 x 9.81 x 4.53)^1/2 = 95.45 m^3/sec

No. of units of saddle siphon = 350 / 95.45 = 3.66 units. = 4 units.