Civil Engineering - UPSC Civil Service Exam Questions - Discussion
Discussion Forum : UPSC Civil Service Exam Questions - Section 3 (Q.No. 46)
46.
At the same mean velocity, what is the ratio of head loss per unit length for a sewer pipe flowing full to that for the same pipe flowing half full ?
Discussion:
6 comments Page 1 of 1.
Rahul verma said:
2 years ago
The correct answer is C.
Rahul verma said:
3 years ago
H = FLV^2/2gD.
D1 = D2
H1 = H2
HEAD LOSS WILL BE EQUAL SO;
RATIO IS 1:1.
D1 = D2
H1 = H2
HEAD LOSS WILL BE EQUAL SO;
RATIO IS 1:1.
Aditya kumar said:
5 years ago
Use the formula:
Hf= flQ^2/12d^5.
Since all other values will be same other than "d"
For 1st condition - headloss =Q^2/d^5 = (A*V)^2/d^5.
For 2nd condition- headloss = (A*v)^2/d^5, where d = d/2.
divide 1 and 2.
So, the answer is 2.
Hf= flQ^2/12d^5.
Since all other values will be same other than "d"
For 1st condition - headloss =Q^2/d^5 = (A*V)^2/d^5.
For 2nd condition- headloss = (A*v)^2/d^5, where d = d/2.
divide 1 and 2.
So, the answer is 2.
Jinish said:
6 years ago
Head loss = v^2/2g and v= q/a and a=3.14xd^2/4.
So, for full flow D=d and half flow = d/2 now substitute value in head loss then ratio. So, it Will be 2.
So, for full flow D=d and half flow = d/2 now substitute value in head loss then ratio. So, it Will be 2.
Siddesh G M said:
7 years ago
Why not C?
Sadashiva said:
7 years ago
Head loss due to friction/unit length of pipe is proportional to mean velocity square V^2 and inversely proportional to the diameter D of the pipe.
V = volumetric flow rate remains same.
So, the head loss due to friction: ratio when flowing full / when flowing half full = 1.
V = volumetric flow rate remains same.
So, the head loss due to friction: ratio when flowing full / when flowing half full = 1.
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