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Day 2 > Fluid Mechanics > Flashcards

Fluid Mechanics Flashcards

1
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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2
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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3
Q

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

A

more than

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4
Q

Which of the following is not concerned with the fluid-particle interaction?
A. Drag co-efficient
B. Froude Number
C. Galileo Number
D. Weber Number

A

Weber Number

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5
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

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6
Q

Brownian movement is prominent in the particle size range of __________ microns in case of settling of a particle in a fluid.

A

2 to 3

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7
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 10-3m. The top plate is moving with a velocity of 1 m/s. The shear stress on the plate is

A

20 Kpa

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8
Q

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

A

Correct

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9
Q

The ratio of maximum to average velocity in case of streamline flow between parallel plates is

A

1.5

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10
Q

The ratio of average fluid velocity to the maximum velocity in case of laminar flow of a Newtonion fluid in a circular pipe is

A

0.5

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11
Q

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

A

Wrong

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12
Q

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

A

2

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13
Q

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

A

0.5d

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14
Q

The ratio of the hydraulic radius to the diameter of the channel, for maximum mean velocity of flow in a circular channel, in open channel flow is

A

0.3

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15
Q

For the free settling of a spherical particle through a fluid, the slope of, CD-log NRe, plot is

A

-1

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16
Q

What is the ratio of total kinetic energy of fluid passing per second to the value obtained on the basis of average velocity (for laminar flow through a circular pipe)?

A

2

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17
Q

The velocity profile exhibited by laminar flow of Newtonion fluids is such that the velocity distribution w.r.t. radius of the circular pipe is a/an __________ with the apex at the centre line of the pipe.

A

Parabola

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18
Q

Upto what value of ‘Mach number’, a fluid may be considered as incompressible ?

A

0.3

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19
Q

Friction losses in pipe fittings are generally expressed in terms of velocity heads.

A

Wrong

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20
Q

Flow rate of high velocity flue gas discharged through a stack to the atmosphere can be most conveniently measured by a

A

Pitot tube

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21
Q

With increase in the ratio of orifice diameter to pipe diameter in case of an orificemeter, the overall pressure loss

A

remains constant

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22
Q

The discharge through a semi-circular weir varies as (where, H = Head of liquid.)

A

H²

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23
Q

The Mach number for hypersonic flow of compressible fluid is

A

> 4

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24
Q

Boundary layer thickness in turbulent flow over a flat plate increases as(where,d= distance from the leading edge.)

A

d^4/5

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25
Q

In centrifugal pump operation, the cavitation can be eliminated by maintaining suction pressure __________ the vapor pressure of the liquid at the suction temperature.

A

higher than

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26
Q

A rectangular surface 3’ x 4’, has the lower 3 edge horizontal and 6’ below a free oil surface (sp. gr. 0.8). The surface inclination is 300 with the horizontal. The force on one side of the surface is(where, y = specific weight of water)

A

48y

27
Q

A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun’s equation for the above fluid-particle system (in SI units) is given below :
Δ P/L = 375 x 103VOM+ 10.94 x 106V2OM(SI units)
If water is to be used as the fluidising medium, the minimum fluidisation velocity, VOMis

A

16 mm/s

28
Q

In case of turbulent flow of a Newtonion fluid in a straight pipe, the maximum velocity is equal to (where,Vavg= average fluid velocity)

A

1.2Vavg

29
Q

For laminar flow of Newtonion fluids through a circular pipe, for a given pressure drop and length & diameter of pipe, the velocity of fluid is proportional to(where, μ = fluid viscosity )

A

1/μ

30
Q

An ideal fluid is the one, which has negligible surface tension and obeys the Newton’s law of viscosity.

A

Wrong

31
Q

For pipe flows, head is proportional to __________ at constant capacity(where,D= pipe diameter).

A

1/D5

32
Q

What is the ratio of fluid carrying capacity of two pipes having diametersd1andd2respectively ?

A

(d1/d2)⁰•⁵

33
Q

In case of a centrifugal pump, the ratio of total delivered pressure to pressure developed with the impeller is called the __________ efficiency.

A

manometric

34
Q

In case of isentropic flow, the speed of sound in an ideal gas is proportional to (where,T= absolute temperature )

A

√T

35
Q

Applying a pressure drop across a capillary results in a volumetric flow rate ‘Q’ under laminar flow conditions. The flow rate for the same pressure drop, in a capillary of the same length but half the radius is

A

Q/16

36
Q

For ideally incompressible fluid, the Mach number will be

A

1

37
Q

In case of isentropic flow, the speed of sound in an ideal gas is proportional to (whereM= molecular weight of the gas)

A

1/√M

38
Q

A mercury (specific gravity = 13.6) manometer connected across an orificemeter fitted in a pipe shows a manometer reading of 2 cms. If the manometer liquid is changed to carbon tetrachloride (specific gravity = 1.6), then for the same flow rate of water the new manometer reading will be __________ cms.

A

17

39
Q

The ratio of wall drag to total drag in the Stoke’s law range is

A

2/3

40
Q

Rotary vacuum pumps can reduce the absolute pressure to as low as __________ mm Hg.

A

0.01

41
Q

A pitched-blade turbine draws __________ a straight blade turbine.

A

less power than

42
Q

A pitched-blade turbine draws __________ a straight blade turbine.

A

ε = ε0+ α.t

43
Q

Nominal size of a pipe is an indication of its __________ diameter.

A

approximate

44
Q

A fluid is pumped at the rate of 10 lb/sec to a height of 55 ft. The horse power required is __________ hp.

A

1

45
Q

The point at which the resultant pressure on an immersed surface acts, is known as the centre of gravity.

A

Wrooooooong

46
Q

In a fully turbulent flow (Re> 105) in a pipe of diameter ‘d’, for a constant pressure gradient, the dependence of volumetric flow rate of an incompressible fluid is

A

d2.5

47
Q

In the Newton’s law range, the terminal velocity of a solid spherical particle falling through a stationary fluid mass is __________ the fluid viscosity.

A

inversely proportional to

48
Q

The exit cone angle in case of a standard venturimeter is __________ the entrance cone angle.

A

smaller than

49
Q

Permanent loss in a venturimeter is about __________ percent of the pressure drop in theupstream cone.

A

10

50
Q

Volume of liquid displaced by a floating body is equivalent to its

A

own weight

51
Q

No shock wave develops in the tube when the Mach number at exit is greater than unity.

A

Correctueee

52
Q

Assuming flow to be laminar, if the diameter of the pipe is halved, then the pressure drop will

A

increase

53
Q

With increase in the ratio of orifice diameter to pipe diameter, the fraction of the orifice pressure differential that is permanently lost

A

decreases

54
Q

The kinetic energy correction factor for velocity distribution of laminar flow is

A

1.66

55
Q

Bed pressure drop in an air fluidised bed of catalyst particles (ρp= 200 kg/m3, Dp= 0.05 cm) of 60 cm bed depth and bed porosity of 0.5 expressed in cm of water (manometer) is

A

60

56
Q

A fluidis moving at critical flow condition (NRe= 2100) through a pipe of dia 3 cms. Velocity of flow is __________ cm/sec.

A

7

57
Q

Capillary rise of mercury in a small diameter tube is proportional to (where,d= diameter of the tube, σ = surface tension of mercury)

A

σ

58
Q

The pressure drop per unit length of pipe incurred by a fluid ‘X’ flowing through pipe is Δp. If another fluid ‘Y’ having both the specific gravity & density just double of that of fluid ‘X’, flows through the same pipe at the same flow rate/average velocity, then the pressure drop in this case will be

A

2Δp

59
Q

In the laminar boundary layer flow over a flat plate, the ratio (δ/x) varies as :(where, ‘δ’ is the boundary layer thickness and ‘x’ is the distance from the leading edge in the direction of flow).

A

Re-1/2

60
Q

A rotameter through which air at room temperature and atmospheric pressure is flowing gives a certain reading for a flow rate of 100 cc/sec. If helium (molecular weight 4) is used and rotameter shows the same reading, the flow rate (cc/sec) is

A

269

61
Q

A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m3) is to be fluidised by water (density 1000 kg/m3). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is

A

4.4 kPa

62
Q

Venturimeter occupies less space than an orificemeter.

A

Wrooonggg

63
Q

Reynolds number for water flow through a tube of I.D. 5 cm is 1500. If a liquid of 5 centipoise viscosity and 0.8 specific gravity flows in the same pipe at the same velocity, then the pressure drop will

A

increase

Day 2 (7 decks)

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