fluid mechanics qp

8/10/2019 FLUID MECHANICS QP

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FLUID MECHANICS

1. Draw a neat sketch of a pitot tube and describe its principle of operation. 5

2. What is priming of pump and why is it necessary to do priming before starting a

centrifugal pump ?5

3. Starting from Eulers e!uation" deri#e the $ernoullis e!uation for potential

flow. 5

%. & long plastic tube with an inside diameter of '(5 mm is connected to a faucet

wherethe pressure of water is 1'' k)a abo#e atmospheric. Estimate the length of the tube

so that the deli#ery is 2(5 lit*day. +he inlet and deli#ery ends of the system are at ground

le#el. &ssume density and #iscosity of water are 1''' kg*m 3 and 1 m)as respecti#ely. 5

5. Deri#e ,agen )oiseuille e!uation relating pressure drop and a#erage #elocity for

laminar flow in a hori-ontal pipe. Eplain its importance. 5

6. & metallic sphere of specific gra#ity /.' falls in an oil of density 0''kg*m3. +he

diameter of the sphere is 0 mm and it attains a terminal #elocity of %'mm*s. indthe #iscosity of the oil in poise. 5

7. %. & man weighing ' kgf descends to the ground from an aeroplane with the helpof a parachute against the resistance of air. +he #elocity with which the parachute"

which is hemispherical in shape" comes down is 2'm*s. ind the diameter. &ssume

D4'.5 and density of air41.25 kg*m3

8. n turbulent flow through a circular pipe deri#e the relation between a#erage

#elocity 67a#g8 and maimum #elocity 67ma8 using the e!uation 7a#g4 7ma1*/

9. & crude oil of #iscosity './ poise and relati#e density '. is flowing through a

hori-ontal circular pipe of diameter 1'' mm and length 1' m. alculate the


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difference of pressure at the two ends of the pipe" if 1'' kg of the oil is collected in

a tank in 3' seconds.

10. /. a8 Distinguish between streamline and streakline.2

b8 9+he pressure drop across a fluidi-ed bed always remains constant:. Eplain thestatement with proper reason.

3

11. Write a short note on the total shear stress in turbulent flow. Write about the )randtl miing lengththeory for turbulent shear stress. 5

12.What is priming of pump and why is it necessary to do priming before starting a

centrifugal pump ; %

b8 What is fluidi-ation ; Write the differences between particulate and bubbling

fluidi-ation. What is minimum fluidi-ation #elocity ; 1 < % < 1

c8 With a neat drawing" eplain the characteristic cur#es of a centrifugal pump . 3

d8 n terms of pressure ratio what is the difference between a blower and a compressor . 2

13. a8 Show that the momentum correction factor and energy correction factor for laminar flow through a

circular pipe are and 2.' respecti#ely.

b8 +hree pipes of %''mm" 2''mm" and 3''mm diameter ha#e lengths of %''m" 2''m" 3''m respecti#ely.

+hey are connected in series to make a compound pipe. +he ends of this compound pipe are connected

with two tanks whose difference of water le#els is 1=m. f co>efficient of friction for these pipes is same

and e!ual to '.''5" determine the discharge through the compound pipe including all the minor losses.

(7+8)

1% a8 & centrifugal fan is used to take flue gas at rest and at a pressure of /3/mm hg and a temperature

of 3.3' and discharge it at a pressure of /=5mm ,g and #elocity of %5./m*s. alculate the power

needed to mo#e 1='m3*h of gas using standard conditions of 2.in ,g and 32'. +he efficiency of the

fan is =5? and the molecular weight of gas is 31.3.


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b8 &n orifice meter with flange tapes is to be installesd in a 1''mm line to measure the flow of water.

+he maimum flow rate is epected to be 5'm3*h at 15'. +he manometer used to measure the differential

pressure is to be filled with mercury" and water is to fill the leads abo#e the surface of the mercury. +he

water temperature will be 15' throughout. 6i8 f the maimum manometer reading is to be 1.25m" what

diameter" to the nearest millimeter" should be specified for the orifice; 6ii8 What will be the power to

operate the meter at full load;

(9+6)

15. a8 Define boundary layer. Discuss briefly about the de#elopment of boundary layer o#er a flat plate.

b8 Determine the thickness of the boundary layer at the trailing edge of smooth plate of length % m and

width 1.5 m" when the plate is mo#ing with a #elocity of % m*s" in stationary air. +ake kinematic #iscosityof air as 1.5 1'>5m2*s.

c8 Discuss the significance of the different terms of @a#ier>Stokes e!uation. (2+3+5+5)

1=8 a8 )articles of sphalerite 6specific gra#ity %.''8are settling under the force of gra#ity in carbon

tetrachloride 6l%8 at 2'' 6 specific gra#ity 1.5%8. +he diameter of the sphalerite particles is '.1'mm.

the #olume fraction of sphalerite in l% is '.2'. What is the settling #elocity of the sphalerite;

b8 & bed of ion>echange beads 0ft deep is to be backwashed with water to remo#e dirt. +he particles

ha#e a density of 1.2%g*cm3and an a#erage si-e of 1.1mm. What is the minimum fluidi-ation #elocity

using water at 2'' " and what #elocity is re!uired to epand the bed by 25?; +he beads are assumed to

be spherical 6s418" and A is taken as '.%'.

c8 Discuss about the utili-ations of a fluidi-ed bed . (5+7+3)

1/. a8 Deri#e the e!uation gi#ing the #elocity distribution at steady state for laminar flow of a constant

density fluid with constant #iscosity flowing between two flat and parallel plates. +he #elocity profile

desired is at a point far from the inlet or outlet of the channel. +he two plates will be considered to be

fied and of infinite width" with the flow dri#en by the pressure gradient in >direction.

b8 With a neat drawing" eplain the characteristic cur#es of a centrifugal pump.

c8 What is non>@ewtonian fluid" gi#e two eamples. (8+5+2)

10. a ) Write about the advantages of triangular notch or weir over Rectangular

Notch or weir.


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b) Water at 202C is pumped at a constant rate of 9 m3/h from a large reservoir resting

on the floor to the open top of an experimental absorption tower. The point of

discharge is 5 m above the floor, and friction losses in the 50 mm pipe from the

reservoir to the tower amount to 25 J/kg. At what height in the reservoir must the

water level be kept if the pump can deliver only 01 kW ? (10+5)

except t!" t#$ te %&e"t!' ppe# '* "t , $e#"

22. Write short notes on $ t#eeof those (5-3)

i8 ,otweir &nimometer

ii8 Cotameter

iii8 &d#antages of a 7>notch o#er a rectangular notch.

i#8 Difference between particulate fluidi-ation and bubbling fluidi-a!tion#8 )riming of a entrifugal pump" and its importance

#i8 )itot tubes.

21.i8 n turbulent flow" the

a8 fluid particles mo#e in an orderly manner. b8 momentum transfer is on molecular scall only.

c8shear stress is caused more effecti#ely by cohesion than momentum transfer.

d8shear stress are generally larger than in a similar laminar flow .

ii8 +he #alue of critical Ceynolds number for pipe flow

a8 13'' b8 1'"'''

c8 1''"''' d8 none of these


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iii8 sotropic turbulence occurs

a8 where there is no #elocity gradient

b8 &t high temperature

c8 on in @ewtonian fluid

d8 none of these

i#8 n laminar flow though a pipe" anning friction factor 6f8 and Ceynolds number 6@ Ce8 are

related by

a8 f4 1=*@ Ce b8 f4 =%*@ Ce

c8 f 4 '.'/* @Ce'.2' d8 f4 '.31= *@ Ce

'.2'

#8 +he ratio of the local #elocity to the maimum #elocity in laminar flow through pipes is gi#en

by

a8 u*u ma4 r*C b8 u*u ma 4 1> 6r*C82

c8 u*u ma4 1>6r*C82 d8 u*u ma4 1>6r*C8

#i8 @a#ier>Stokes e!uation deals with the law of conser#ation of

a8 Aass

b8 Energyc8 Aomentum

d8 $oth 6a8 and 6b8

#ii8 or an ideal fluid flow" Ceynolds number isa8 21''

b8 1''c8 'd8 nfinity

#iii8 +ooth paste is an eample ofa8 $ingham plastic fluid

b8 Dilatants fluid

c8 )seudo plastic


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d8 @ewtonian fluid

i8 )riming is needed in a

a8 Ceciprocating )ump

b8 entrifugal )umpc8 Fear )ump

d8 Diaphragm )ump

8 & fluid is a substance that

a8 has to be kept in a closed container

b8 is almost compressiblec8 has -ero shear stress

d8 lows when e#en a small shear is applied to it

i8 or pumping slurry" one can use GGGGG a pumpa8 )lunger

b8 entrifugalc8 Diaphragm

d8 )neumatic

ii8 +he pressure loss is maimum ina8 #enture meter b8 orifice meter

c8 rotameter d8 flow no--le

iii8 Which of the #ow measuring devices is used to measure #ow rates in anopen channel

a) Rotameter b) 4ilot tube

c) weir d)none of these

i#8 )ower re!uired by a centrifugal pump is proportional toH

a8 @2 D3 b8 @D2

c8 @3D5 d8 @2 D

#8 a#itation in a centrifugal pump can be a#oided by keeping the"

a8 inlet pressure high b8 outlet pressure high

c8 inlet pressure low d8 outlet pressure low


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#i 8 Slugging in a fluidi-ed bed can be a#oided by using

a8 tall narrow #essel

b8 deep bed of solids

c8 shallow beds of solid B proper choice of particle si-e

d8 #ery large particles

fluid mechanics qp

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