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ChE topnotcher class > Momentum > Flashcards

Momentum Flashcards

1
Q

The fluid property, due to which, mercury does not wet the glass is

A

surface tension IE
cohesion CORRECT

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2
Q

When the momentum of one fluid is used for moving another fluid, such a device is called a/an

A

Jet pump

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3
Q

The normal stress is the same in all directions at a point in a fluid, when the fluid is

non-viscous.
incompressible.
both (a) and (b).
having no motion of one fluid layer relative to the other

A

having no motion of one fluid layer relative to the other.

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4
Q

Head developed by a centrifugal pump depends on its

speed
impeller diameter
both (a) and (b)
neither (a) nor (b)

A

Both a and b

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5
Q

Hydraulic mean depth (Dm) for a circular pipe of diameter ‘D’ flowing full is 0.25 D. For a circular channel, at Dm = 0.3 D, gives the condition for the maximum

A

mean velocity

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6
Q

The head loss in turbulent flow in a pipe varies

A

as (velocity)2

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7
Q

Most commonly used joint in the underground pipe lines is the

A

Sleevejoint

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8
Q

Schedule number of a pipe, which is a measure of its wall thickness, is given by

A
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9
Q

The net positive suction head (NPSH) of a centrifugal pump is defined as

A

sum of the velocity head and the pressure head at the suction minus vapor pressure of the liquid at suction temperature.

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10
Q

With increasing flow rate, the hydraulic efficiency of a centrifugal pump

A

monotonically decreases. IE

increases and then decreases. CORRECT

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11
Q

The velocity profile for turbulent flow through a closed conduit is

A

For turbulent its logarithmic.

And for laminar its parabolic

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12
Q

In case of hydraulically smooth pipe, the resistance to flow depends only on the Reynolds number, whereas for a hydraulically rough pipe, the resistance to flow is governed by the relative roughness. Two pipes are said to have the same hydraulic roughness, when they have equal values of

relative roughness.
absolute roughness.
friction co-efficient for flows at equal Reynold number.
all (a), (b) & (c).

A

friction co-efficient for flows at equal Reynold number.

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13
Q

Water hammer in a pipeline results from the

A

rapid pressure change due to a rapid change in the rate of flow.

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14
Q

Molten soap mass is transported by a __________ pump.

A

Gear pump

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15
Q

Which of the following denotes the effect of compressibility in fluid flow ?

A

Mach

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16
Q

Nominal size of the discharge pipe of a pump is usually __________ the nominal size of the inlet pipe.

A

smaller than

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17
Q

The terminal velocity of a small sphere settling in a viscous fluid varies as the
first power of its dimeter.
inverse of the fluid viscosity.
inverse square of the diameter.
square of the difference in specific weights of solid & fluid.

A

inverse of the fluid viscosity

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18
Q

If the discharge of a centrifugal pump is throttled, then its suction lift

A

increases

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19
Q

Foot valves provided in pumps are __________ valves.

A

directional control

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20
Q

At high Reynolds number

A

inertial forces control and viscous forces are unimportant.

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21
Q

Power loss in an orificemeter is __________ that in a venturimeter.

A

more than

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22
Q

The terminal velocity of a particle moving through a fluid varies as dpn. What is the value of n’ for Newton’s law regime ?

A

0.5
Eq 6-239

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23
Q

What is the normal range of exit cone angle of a venturimeter ?

A

7 to 15
Convergent side 15 to 20 and divergent side 5 to 7 in venturi meter.

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24
Q

The dimension of dynamic viscosity is

A

ML-1T-1

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25
Q

A particle A of diameter 10 microns settles in an oil of specific gravity 0.9 and viscosity 10 poise under Stoke’s law. A particle B with diameter 20 microns settling in the same oil will have a settling velocity

same as that of A.
one fourth as that of A.
twice as that of A.
four times as that of A.

A

one fourth as that of A.IE

four times as that of A.

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26
Q

The pitot static tube does not measure the __________ pressure.

static
total
difference in static & dynamic
all (a), (b) and (c)

A

all (a), (b) and (c)

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27
Q

The fluid in which the shearing stress within it is proportional to the velocity gradient across the sheared section, is called a __________ fluid.

A

Newtonion

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28
Q

In fluid flow, cavitation is caused, if the

fluid velocity decreases to zero.
total energy decreases.
both (a) and (b).
flow pressure approaches its vapor pressure at the prevailing temperature.

A

flow pressure approaches its vapor pressure at the prevailing temperature.

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29
Q

The ratio of the depth of flow to the hydraulic radius for the most economical trapezoidal section, in open channel flow is

A

2

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30
Q

The drag co-efficient for a bacterium moving in water at 1 mm/s, will be of the following order of magnitude (assume size of the bacterium to be 1 micron and kinematic viscosity of water to be 10-6m2/s).

A

0.44

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31
Q

For Laminar flow through a packed bed, the pressure drop is proportional to (Vs is the superficial liquid velocity and Dp is the particle diameter)

Vs/Dp2
Vs2/Dp2
Vs2/Dp3
Vs/Dp3

A

Vs/Dp2

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32
Q

The maximum delivery pressure of compressors can be upto __________ atmospheres.

A

1000

33
Q

Co-efficient of velocity is __________ the coefficient of discharge.
less than

less than
more than
equal to
not related to

A

More than

34
Q

All pipes of a particular nominal size have the same

A

outside diameter

35
Q

For the transfer of solution of thick slurry, the pump used is a __________ pump.

A

Diaphragm

36
Q

Which of the following is not concerned with the fluid-particle interaction ?
Drag co-efficient
Froude number
Galileo number
Weber number

A

Weber number

37
Q

Maximum theoretical suction lift for water at 15°C by a centrifugal pump is 34 ft. The same for water at 90°C will be __________ ft.

A

8

38
Q

Pick out the wrong statement.
Momentum transfer in laminar flow results from veclocity gradient.
A fluid in equilibrium is not free from shear stress.
The viscosity of a non-Newtonion fluid is a function of temperature only.
both (b) and (c)

A

both (b) and (c)

39
Q

Pressure drag does not depend upon the
roughness of surface of the body.
pressure of main flow only.
length of the body in flow direction.
all (a), (b) and (c)

A

all (a), (b) and (c)

40
Q

Dimension of absolute viscosity is

A

ML-1T-1
Dynamic is same as absolute
Empirical same with kinematic

41
Q

__________ pumps are axial flow pumps.
Turbine
Propeller
Diffuser
none of these

A

Propeller

42
Q

Brownian movement is prominent in the particle size range of __________ microns in case of settling of a particle in a fluid.
2 to 3
0.01 to 0.10
200 to 300
100 to 1000

A

2 to 3

43
Q

For a particle settling in water at its terminal settling velocity, which of the following is true ?

Buoyancy = weight + drag
Weight = buoyancy + drag
Drag = buoyancy + weight
Drag = weight

A

Weight = buoyancy + drag

44
Q

A Bingham fluid of viscosity μ = 10 Pa.s and yield stress, τ0 = 10 KPa, is shared between flat parallel plates separated by a distance of 10-3 m. The top plate is moving with a velocity of 1 m/s. The shear stress on the plate is

A

20kPa

45
Q

Pick out the correct statement.
A forced vortex occurs when fluid rotates as a solid about an axis.
In laminar flow, Newton’s law of viscosity does not apply.
A free vortex occurs, when fluidrotates as a solid.
In turbulent flow, there are neither cross-currents nor eddies.

A

A forced vortex occurs when fluid rotates as a solid about an axis.

46
Q

Shear stress in a fluid flowing in a round pipe

A

is zero at the centre and varies linearly with the radius.

47
Q

The resistance wire used in a hot wire anemometer for conducting electrical current is made of

A

tungsten

48
Q

Two dimensional stream function

A

is constant along a stream line.

49
Q

What causes cavitation in centrifugal pump ?
High suction pressure
Low barometric pressure
Low suction pressure
High suction velocity

A

Low suction pressure

50
Q

Draining of shallow pits or sump is done by a sump pump, which is a __________ pump

A

single stage vertical

51
Q

A hydraulic ram acts as a/an __________ pump.

A

impulse

52
Q

Pick out the wrong statement.
The shear stress at the pipe (dia = D, length = L) wall in case of laminar flow of Newtonion fluids is
In the equation, the value of ‘n’ for pseudoplastic and dilatant fluids are < 1 and >1 respectively.
Shear stress for Newtonion fluid is proportional to the rate of shear in the direction perpendicular to motion.
With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids.

A

With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids.

53
Q

The line of action of the buoyant force passes through the centre of gravity of the

submerged body.
displaced volume of the fluid.
volume of fluid vertically above the body.
horizontal projection of the body.

A

displaced volume of the fluid.

54
Q

The pressure at a point in a fluid is not the same in all directions, when the fluid is viscous and

A

moving

55
Q

What causes convective acceleration in fluid flow ?

A

Non-uniformity of flow

56
Q

The Stoke’s stream function applies to the
irrotational flow only.
ideal/non-viscous fluids only.
cases of axial symmetry.
none of these.

A

cases of axial symmetry.

57
Q

Slugging in a fluidised bed can be avoided by using

tall narrow vessel.
deep bed of of solids
shallow beds of solids and proper choice of particle size.
very large particles.

A

shallow beds of solids and proper choice of particle size.

58
Q

The ratio of width to depth for the most economical rectangular section in open channel flow is

A

2

59
Q

The simple pitot tube measures the __________ pressure.

static
dynamic
total
none of these

A

Total

60
Q

Capacity of a hydraulic accumulator is defined in terms of maximum
amount of energy stored.
flow rate through accumulator.
rate of falling of ram.
volume available in the cylinder.

A

amount of energy stored.

61
Q

Three piping networks as shown in the figure are placed horizontally. They are made using identical pipe segments and are subjected to the same pressure drop across them. Assuming no pressure losses at junctions, the flow rates across the three networks are related as Q1 : Q2 : Q3.

A

1:2:2

62
Q

With diminishing cross-sectional area in case of subsonic flow in a converging nozzle, the
velocity increases
pressure decreases
both (a) & (b)
neither (a) nor (b)

A

both (a) & (b)

63
Q

Boundary layer separation is characterised by one of the conditions given below, where ‘Re’ is the Reynolds number for the flow. Select the appropriate conditions.

Re &laquo_space;1, accelerating flow
Re&raquo_space; 1, accelerating flow
Re &laquo_space;1, decelerating flow
Re&raquo_space;1, decelerating flow

A

Re&raquo_space;1, decelerating flow

64
Q

Manometers measure the __________ pressure.
vacuum as well as the atmospheric
difference in
absolute
gage

A

difference in

65
Q

Which of the following fluid forces are not considered in the Navier-Stoke’s equation?
Gravity forces
Viscous forces
Pressure forces
Turbulent forces

A

Turbulent forces 6-27 eqn

66
Q

Which of the following may be termed as a variable orifice flowmeter ?
Rotameter
Pitot tube
V-notch
All (a), (b) and (c)

A

Rotameter

67
Q

In turbulent flow, a rough pipe has the same friction factor as a smooth pipe
in the zone of complete turbulence.
when the roughness projections are much smaller than the thickness of the laminar film.
everywhere in the transition zone.
when the friction factor is independent of the Reynold’s number.

A

when the roughness projections are much smaller than the thickness of the laminar film.

68
Q

Air vessel provided in a reciprocating pump
smoothens the flow by avoiding pulsations.
increases the volumetric efficiency of the pump.
saves the pump from the danger of cavitation.
none of these.

A

none of these.

69
Q

Bernoulli’s equation is dependent on the
first law of thermodynamics.
third law of thermodynamics.
law of conservation of momentum.
none of these.

A

first law of thermodynamics

70
Q

For turbulent fluid flow in pipe, the expression for Prandtl one seventh power law is (where, r = pipe radius, x = distance).

A

V/vmax =(x/r)^¹/⁷

71
Q

The capacity of an accumulator is the maximum

A

energy which it can store.

72
Q

Vena-contracta pressure tapping is at a distance __________ from the position of an orificemeter fitted in a pipe of internal diameter ‘d’

A

0.5 d

73
Q

The pump impeller and the turbine runner in a hydraulic torque converter
have the same diameter.
have different diameters.
are directly coupled.
none of these.

A

have different diameters.

74
Q

Reciprocating pumps compared to centrifugal pumps

deliver liquid at uniform pressure.
can handle slurries more efficiently.
are not subject to air binding.
can be operated with delivery valve closed.

A

are not subject to air binding.

75
Q

The fluid property which matters for fall-ing rain drops to acquire spherical shape is its

A

surface tension

76
Q

The simple pitot tube does not measure the
static pressure.
dynamic pressure.
velocity at the stagnation point.
all (a), (b) and (c).

A

all (a), (b) and (c).

77
Q

Boundary layer separation occurs when the

A

cross-section of the channel is reduced.

78
Q

The head loss in turbulent flow in a pipe varies

A

approximately as the square of the velocity.

ChE topnotcher class (6 decks)

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