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Fluid Mechanics > section 4 > Flashcards

section 4 Flashcards

1
Q

Pascal law is not applicable for a/an __________ fluid.
a. accelerating frictionless
b. static
c. uniformly moving
d. none of these

A

d

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2
Q

In a fluidised bed reactor
a. temperature gradients are very high.
b. temperature is more or less uniform.
c. hot spots are formed.
d. segregation of the solids occurs.

A

b

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3
Q

The flow of a liquid through tapering pipe at a constant rate is an example of __________ flow.
a. steady uniform
b. steady non uniform
c. unsteady uniform
d. unsteady non uniform

A

b

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4
Q

Pick out the correct statement pertaining to transition/ entrance length in fluid flow.
aThe length of entrance region of pipe, in which full development of fluid flow takes place such that velocity profile does not change downstream, is called the transition length.
b. Transition length for laminar flow of Newtonion fluids in a pipe of diameter ‘d’ is equal to 0.05. D.NRe.
c. Transition length for turbulent flow of Newtonion fluids in a smooth pipe of diameter ‘d’ is equal to 50 D.
d. all (a), (b) and (c).

A

d

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5
Q

A perfect gas
a. does not satisfy PV= nRT.
b. is incompressible and has zero viscosity.
c. has constant specific heat.
d. can’t develop shear stresses.

A

c

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6
Q

In a/an __________ , the flow rate of fluids is obtained by measuring the difference between the impact and the static pressure.
a. rotameter
b. pitot tube
c. venturimeter
d. flow nozzle

A

b

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7
Q

word

A
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8
Q

Speed of sound in an ideal gas depends on its
a. temperature
b. pressure
c. specific volume
d. none of these

A

a

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9
Q

A centrifugal pump designed for handling water (μ = 1 cp) will deliver __________ when pumping a thicker oil (μ = 30 cp).
a. less head & capacity
b. more head
c. more capacity
d. less head & more capacity

A

a

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10
Q

If ‘x’ is the depth of flow in an open channel of large width, then the hydraulic radius is equal to
a. x
b. x/2
c. x/3
d. 2x/3

A

a

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11
Q

In fluid flow, the boundary layer separation can not occur
a. in case of boundaries experiencing form drag.
b. at points of abrupt changes in the flow directions.
c. in laminar flow.
d. none of these.

A

d

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12
Q

For a given fluid flow rate, which of the following incurs maximum head loss ?
a. Orifice meter
b. Venturimeter
c. Flow nozzle
d. All of them incur the same head loss

A

a

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13
Q

Which of the following assumptions enables the Euler’s equation of motion to be integrated ?
a. The fluid is incompressible.
b. The fluid is non-viscous.
c. The continuity equation is satisfied.
d. The flow is rotational and incompressible.

A

a

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14
Q

In case of a pipe exit fitted with a nozzle, the
a. conversion of kinetic head to pressure head is facilitated.
b. conversion of pressure head to kinetic head is facilitated.
c. power transmitted through the nozzle is maximum, when the head lost due to friction in the pipe is equal to one third of the total supply head.
d. both (b) and (c)

A

d

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15
Q

A fluid whose apparent viscosity increases with shear rate is termed as the __________ fluid.
a. Newtonion
b. viscous
c. dilatant
d. non-viscous

A

c

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16
Q

Which of the following is the most common pump for pumping either raw sewage or sludge ?
a. Electromagnetic pump
b. Centrifugal pump
c. Reciprocating pump
d. Gear pump

A

c

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17
Q

Transition length for a turbulent fluid entering into a pipe is around __________ times the pipe diameter.
a. 5
b. 50
c. 500
d. 1000

A

b

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18
Q

Reciprocating pumps are not able to compete with the centrifugal pump for industrial use, mainly because these pumps have
a. very low speeds.
b. smaller discharge.
c. higher capital &maintenance cost.
d. high vibrations.

A

c

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19
Q

For turbulent flow of an incompressible fluid through a pipe, the flow rate Q is proportional to (Δ P)n, where ΔP is the pressure drop. The value of exponent ‘n’ is
a. 1
b. 0
c. < 1
d. > 1

A

c

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20
Q

Which is the correct relationship for a centrifugal pump ? (where, D = Impeller diameter, inches H = Head developed, ft of liquid pumped N = Speed of pump, rpm)
a. D = 1840 H0.5/N
b. D = 1840 N/H0.5
c. H = 1840 D0.5/N
d. D = 1840 H/N

A

a

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21
Q

Which of the following pipe bends will incur the largest head loss ?
a. U-bend
b. 30° bend
c. 45° bend
d. 90° bend

A

a

22
Q

Which is the most efficient and best for measuring very small flow rate of gases ?
a. Venturimeter
b. Orifice meter
c. Rotameter
d. Flow nozzle

A

c

23
Q

When the water is warm, the height to which it can be lifted by a pump
a. decreases due to reduced viscosity.
b. decreases due to reduced vapour pressure.
c. increases due to increased vapour pressure
d. decreases due to increased frictional resistance.

A

b

24
Q

Pipes having diameter 14 inches or more are designated by their
a. outside diameter
b. inside diameter
c. schedule number
d, none of these

A

a

25
Q

Viscosity of water at 40°C lies in the range of
a. 1 x 10-3 to 2 x 10-3 kg/m.s
b. 0.5 x 10-3 to 1 x 10-3 kg/m.s
c. 1 to 2 kg/m.s
d. 0.5 to 1 kg/m.s

A

b

26
Q

A centrifugal pump has the following specifications:
Power = 4 H.P.; Speed = 800 rpm
Head = 8 metres
Flow = 1000 litres/minutes.
If its speed is halved, the new discharge will be __________ litres/minute.
a. 500
b. 200
c. 1000
d. 750

A

a

27
Q

The dimension of kinematic viscosity is
a. ML-2T-1
b. L2T-1
c. ML-2T-2
d. none of these

A

b

28
Q

A pipe of I.D. 4 m is bifurcated into two pipes of I.D. 2 m each. If the average velocity of water flowing through the main pipe is 5 m/sec, the average velocity through the bifurcated pipes is
a. 20 m/sec
b. 10 m/sec
c. 52 m/sec
d. 5 m/sec

A

b

29
Q

Lower BWG means __________ of the tube.
a. lower thickness
b. lower cross-section
c. outer diameter
d. inner diameter

A

b

29
Q

Turbulent flow generally occurs for cases involving
a. highly viscous fluid
b. very narrow passages
c. very slow motion
d. none of these

A

d

30
Q

For laminar flow of Newtonion fluid in a circular pipe, the velocity distribution is a function of the distance ‘d’ measured from the centre line of the pipe, and it follows a __________ relationship.
a. logarithmic
b. parabolic
c. hyperbolic
d. linear

A

b

31
Q

The Prandtl mixing length is
a. zero at the pipe wall and is a universal constant.
b. independent of radial distance from the pipe axis.
c. independent of the shear stress.
d. useful for computing laminar flow problems.

A

d

32
Q

N2Re/NFr is called the __________ number.
a. Brinkman
b. Galileo
c. Archimedes
d. Euler

A

b

33
Q

The location of centre of pressure, which defines the point of application of the total pressure force on the surface, can be calculated by applying the principle of moments according to which “sum of the moment of the resultant force about an axis is equal to the sum of the components about the same axis”. The centre of pressure of a rectangular surface (of width ‘w’) immersed vertically in a static mass of fluid is at a depth of(where, y = depth of the liquid)
a. 1/y/3
b. 2y/3
c. 1/y/4
d. 3y/4

A

b

34
Q

As the velocity V and thus the Reynolds number of a flow past a sphere increases from very low value, the drag force for Re &laquo_space;1
a. increases linearly with V.
b. decreases linearly with V.
c. decreases as V2.
d. none of these.

A

a

35
Q

Self-priming centrifugal pump can be used for
a. booster service.
b. pumping liquid fertilisers (e.g. liquid NH3).
c. pumping industrial wastes.
d. all (a), (b) and (c).

A

d

36
Q

Water hammer is caused, when water flowing in a pipe is suddenly brought to rest by closing the valve. The extent of pressure thus produced due to water hammer depends on the
a. pipe length
b. fluid velocity in the pipe
c. time taken to close the valve
d. all (a), (b) and (c)

A

d

37
Q

Bernoull’s equation does not apply to the functioning of a/an
a. venturimeter
b. orificem
c. pitot tube
d. none of these

A

d

38
Q

What is the shear rate at the pipe wall, in case of laminar flow of Newtonion fluids in a pipe of diameter ‘D’ & length ‘L’ incurring a pressure drop ‘Δp’ with average velocity ‘Vavg’?
a. D Δp/8L
b. D Δp/4L
c. 8 . Vavg/D
d. 4 . Vavg/D

A

c

39
Q

Pascal’s law is valid, only when the fluid is
a. frictionless and at rest.
b. at rest.
c. at rest and when the frictionless fluid is in motion.
d. none of these.

A

b

40
Q

word

A
41
Q

The pressure head of a flow meter remains constant for
a. venturimeter
b. orificemeter
c. rotameter
d. pitot tube

A

c

42
Q

A venturimeter can not be used for the direct measurement of
a. datum difference in the stretch of pipeflow
b. pressure difference in the flow throughpipeline.
c. friction loss in pipe flow.
d. all (a), (b) and (c).

A

d

43
Q

A double acting reciprocating pump compared to a single acting pump (of almost same size working under same pressure levels) would give almost double
a. head
b. discharge
c. efficiency
d. none of these

A

b

44
Q

Which of the following is used for very accurate measurement of flow of gas at low velocity ?
a. Pitot tube
b. Rotameter
c. Segmental orificemeter
d. Hot wire annemometer

A

d

45
Q

The rate of shear versus the shear stress curves are time dependent for __________ fluid.
a. thixotropic
b. rheopectic
c. both (a) & (b)
d. neither (a) nor (b)

A

c

46
Q

In Newton’s law range, the drag co-efficient for the motion of spherical particle in a stationary fluid is
a. 0.44
b. 0.044
c. 4.4
d. 44

A

a

47
Q

A pressure of 10 m head of water is equivalent to __________ kN/m2.
a. 98
b. 147
c. 196
d. 49

A

a

48
Q

A pressure head of 320 metres of water in meters of CCl4 (sp.gr = 1.6) will be
a. 100
b. 200
c. 320
d. 160

A

b

49
Q

word

A

Fluid Mechanics (4 decks)

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