Civil Engineering - UPSC Civil Service Exam Questions - Discussion

12. 

The discharge per metre width at the foot of a spillway is 10 m3/s at a velocity of 20 m/s. A perfect free hydraulic jump will occur at the foot of the spillway when the tail water depth is approximately equal to

[A]. 4.50 m
[B]. 5.00 m
[C]. 5.50 m
[D]. 6.50 m

Answer: Option D

Explanation:

No answer description available for this question.

Danesh said: (Sep 24, 2013)  
V*Y = q.

From here y1 = 0.5.

Now, y2 = (y1/2)*((sq rt of 1+8F^2)-1).

Abhay said: (Feb 3, 2016)  
Discharge Q = Velocity * Head (or water depth).

Q = 10 m^3/s.

v = 20 m/s.

h1 = 10/20 = 0.5 m.

The jump will occur if and only if the level of inflowing (supercritical) water level (h_0) satisfies the condition:

h0/h1 = [-1 + √(1 + 8v^2/(9.81 * h1))]/2.

h0/0.5 = [-1 + √(1 + 8*20^2/(9.81*0.5))]/2 = 3.32.

h0 = 6.64 m.

Mohsin said: (Apr 5, 2018)  
@All.
Discharge = velocity x area.
area= width x height.
In question discharge per meter width is given as 10 cms, therefore,
Unit width discharge = velocity x height.

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