Andhra University 2007-1st Year B.E Civil Engineering I ./B.Tech FLUID MECHANICS - I - Question Paper

II Year B.E./B.Tech Degree exam

FLUID MECHANICS - I

(Civil Engineering)

Time : 3 hours Maximum : 75 Marks

ques. one is compulsory

ans any 4 from ques. two to 8.

All ques. carry equal marks

9

(c) Distinguish ranging from Surface forces and body forces

(4 marks)

3. (a) Arrive at the condition for irrotationality of an ideal fluid in

terms of the velocity gradients. (5 Marks)

(b) What is the significance of energy correction factor in

Bernoullis equation? Arrive at the expression for the identical.

(6 Marks)

(c) discuss the importance of flow net in engineering applications.

(4 Marks)

4. (a) An oil of sp. gr. 0.90 flows through a vertical pipe of diameter

20cm. The flow is measured by a 20cmx10cm

venturimeter. The throat is 10cm above the inlet. A differential

U-tube mercury manometer is connected to the

Venturimeter. If Cd = 0.99, what is (a) the flow for a manometer

studying of nine cm and (b) the manometer studying for

a flow of 50 lps ? (8 Marks)

(b) Derive the expression for emptying a hemispherical tank of

radius ‘R’ through an orifice of area ‘a’ whose coefficient of

discharge is Cd.

5. (a) State the laws of friction for turbulent flow in a pipe. (4Marks)

(b) A concrete pipe 90 cm in diameter and 20 m long is used as a

culvert. The pipe is laid on a slope of one in 60 and has square

entrance. During a heavy flow of 1.50m 3/s, if the culvert is

submerged and the depth of flow over the invert at the downstream

end is 1.25 m, estimate the depth of water above the pipe

invert at the upstream end. [Assume f =0.025] (7 Marks)

(c) Derive the expression for loss of head due to sudden contraction

in a pipe. (4 Marks)

6. (a) Water from a reservoir flows through a pipe line of length L

10

and diameter d and discharges though a nozzle of diameter

dn. If the loss of head in the nozzle is K [V 2

n / 2g ] where

K= constant and Vn = velocity in the nozzle. Show that for

maximum power transmission through the pipeline is

( ) 1

1 4

2

n d k d

d fL

é+ ù

=ê ú

ë û

where f is the friction coefficient for the pipe.

(b) Water is discharged from a reservoir into the atmosphere

through a pipe 39 m long. There is a sharp entrance to the

pipe and the diameter is 50 mm for 15 m from the entrance.

The pipe then enlarges suddenly to 75 mm in diameter for

the reminder of its length. Taking into account the loss of

head at entry, enlargement, compute the difference of level

ranging from the water surface of the resevoir and the pipe exit

which will maintain a flow of 2.8 Its/sec. Take f = 0.02 for

50 mm pipe and 0.025 for 75 mm pipe. Draw also HGL

and total energy gradient lines.

7. (a) discuss the Weber legal regulations of likeness. (4 Marks)

(b) Show that the total resistance R of a floating ship is provided by

the expression 3

1

1 fs

f

r fm

C

R r r

l C

é æ öù

= êêë+ ççè -÷÷øúúû

where lr is the

scale ratio, r is the total resistance on the model, rf is the

frictional resistance on the model and Cfs and Cfm are the
frictional coefficients for the ship and its model respectively.

It may be presumed that the ship and the model are towed in

the identical water. (6 Marks)

(c) A spillway model is to be built to a geometrically similar

scale of 1/50 across a flume of 60 cm width.The prototype

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is 15m high and the maximum head on it is expected to be

1.5m. (i) What height of model and what head off the model

should be used? (ii) If the flow over the model at a particular

head is 12 lps, what flow per meter width of the prototype

is expected ? (iii) If the negative pressure in the model is 20
cm, what is the negative pressure in the prototype ? Is it

practical ? (5 Marks)

8. Write short notes on any 3 (3x5 = 15 Marks)

(a) Flow net (b) Pipes in parallel (c) Syphon

(d) Reynolds experiment (e) Distorted models (f) Lock gates

Earning:   Approval pending.