Quiznetik

Fluid Mechanics and Hydraulic Machines | Set 2

1. The laminar/viscous flow is characterized by Reynolds number which is

Correct : A. less than the critical value

2. The laminar flow is characterized by

Correct : C. Fluid particles moving in layers parallel to the boundary surface

3. In case of laminar flow, the loss of pressure head is proportional to

Correct : A. Velocity

4. The pressure gradient in the direction of flow is equal to the shear gradient in the direction

Correct : B. Normal to the direction of flow

5. …... studied the laminar flow through a circular tube experimentally

Correct : C. Hagen and Poiseuille

6. …... is the most commonly used equation for the velocity distribution for laminar flow through pipes.

Correct : B. u = umax [1- (r/R)2]

7. In laminar flow the pressure drop per unit length of pipe (∆p/L) is given as

Correct : A. 32𝜇͞u/D2

8. The K.E. correction factor a for a circular pipe is equal to

Correct : A. 2

9. The momentum correction factor b for a circular pipe is to equal to

Correct : C. 4/3

10. For viscous flow the co-efficient of friction is given by

Correct : B. f = 16/Re

11. In case of viscous flow through circular pipes

Correct : B. u = (3/2) umax

12. The maximum velocity in a circular pipe when flow is laminar occurs at

Correct : C. The centre of the pipe

13. The flow is said to be turbulent when Reynolds number is

Correct : C. Greater than 4000

14. The shear in turbulent flow is mainly due to

Correct : C. Momentum transfer

15. Which of the following statements is correct? Wall turbulence occurs

Correct : A. In immediate vicinity of solid surfaces and in the boundary layer flows where the fluid has a negligible mean acceleration

16. The flow in town water supply pipes is generally

Correct : B. Turbulent

17. The most essential feature of a turbulent flow is

Correct : D. Velocity and pressure at a point exhibit irregular fluctuations of high frequency.

18. In turbulent flow the velocity distribution is a function of the distance y measured from the boundary surface and shear friction velocity uf, and follows a

Correct : D. Logarithmic law.

19. A turbulent flow is considered steady when

Correct : C. Temporal mean velocity at a point remains constant with time

20. The Darcy-Weisbach friction factor f which is a direct measure of resistance to flow in pipes depends on which of the following?

Correct : D. Roughness height, diameter, velocity and kinematic viscosity.

21. Commercial cast-iron and steel pipes carrying fluids under pressure are regarded as hydraulically smooth when

Correct : C. The roughness elements are all completely covered by the laminar sublayer

22. Intensity of turbulence is

Correct : B. The violence of turbulent fluctuations and is measured by the root mean square value of velocity fluctuations

23. Which of the following factors determine the friction factor for turbulent flow in a rough pipe?

Correct : C. Reynolds number and relative roughness

24. In case of turbulent flow of a fluid through a circular tube (as compared to the case of laminar flow at the same flow rate) the maximum velocity is ....., shear stress at the wall is ....., and the pressure drop across a given length is ....., the correct words for the blanks are, respectively

Correct : B. lower, higher, higher

25. In a laminar flow, Reynold’s number is

Correct : A. Less than 2000

26. In a turbulent flow, Reynold’s number is

Correct : B. More than 4000

27. In case of a laminar flow, the loss of pressure head is

Correct : B. Proportional to velocity

28. In case of a turbulent flow, the loss of head is approximately proportional to

Correct : D. (Velocity) ^2

29. Darcy-Weisbach equation is used to find loss of head due to :

Correct : C. Friction

30. Chezy’s formula is given as

Correct : C. V = C√𝑚𝑖

31. Loss of head due to sudden enlargement is given as

Correct : B. (𝑉1−𝑉2)22𝑔

32. 2𝑔 148. The power transmitted through the pipe is maximum when head lost due to friction in the pipe is equal to

Correct : C. (1/5) th of the total supply head

33. The energy loss in a pipeline is due to

Correct : C. Friction offered by pipe wall as well as by viscous function

34. In a pipe flow the minor losses are those

Correct : D. Which are caused on account of total disturbance produced by such fittings as valves, bends, etc.

35. In flow through pipe bends the pressures on inner and out radii

Correct : D. Do not vary and are the same as at the center of the pipe.

36. The condition for maximum transmission of power through a pipeline is that one-third of the available head must be consumed in friction. The corresponding efficiency of the pipeline is

Correct : B. 66·67%

37. For achieving continuous flow through a system, no position of the pipe should be higher than

Correct : C. 7·6 m

38. For turbulent flow in smooth pipes, the entrance length is taken as

Correct : B. 50

39. The entrance length or length of establishment of flow is

Correct : D. The initial length in which the flow develops fully such that the velocity profile does not change downstream.

40. Due to which of the following phenomena water hammer is caused?

Correct : D. Sudden closure (partial or complete) of a valve in pipe flow.

41. Under which of the following conditions the closure of valve is considered rapid? (where L = length of pipe, C = velocity of pressure wave produced due to water hammer.)

Correct : C. The duration of valve closure is less than 2L/C

42. The force exerted by a jet of water on a moving vertical plate, in the direction of motion of plate is given by

Correct : C. ρa (V – u)2

43. When a steady jet impinges on a fixed inclined surface

Correct : A. The flow is divided into parts proportional to the angle of inclination of the surface

44. For maximum efficiency of a series of curved vanes, the speed is

Correct : C. 1/2 of the jet speed

45. The efficiency of jet propulsion with inlet orifices at right angles to the direction of motion of ship is given by

Correct : B. 2V/ (V + u) 2

46. For an impulse turbine which of the following statements is correct :

Correct : D. It operates with initial complete conversion of pressure head to velocity head.

47. Which of the following statements is correct in case of a Pelton wheel :

Correct : D. It operates by converting the available energy fully into kinetic energy before entering the rotor.

48. The effective (or net) head at the turbine is

Correct : C. The difference between the gross head minus head loss in penstock and the velocity head at the turbine exit

49. The difference between the power obtained from the turbine shaft and power supplied by water at its entry to the turbine is equal to

Correct : A. Sum of hydraulic and mechanical losses

50. Which of the following statements is a definition of the hydraulic efficiency of a turbine?

Correct : C. The ratio of power utilized by runner to that supplied by the water at entry to the turbine.

51. The power which appears in the expression for the specific speed is the:

Correct : A. Shaft power

52. Which of the following statements is correct: Runaway speed of a hydraulic turbine is the speed

Correct : B. At which the turbine runner can be allowed to run freely without load and with wicket gates wide open

53. Which of the following statements is correct for a reaction turbine?

Correct : D. There is only partial conversion of available head to velocity head before entry to rotor.

54. In a reaction turbine the function of a draft tube is to

Correct : C. Reconvert the kinetic energy to flow energy

55. Which of the following statements with respect to a reaction water turbine is incorrect:

Correct : B. The water leaves the turbine at atmospheric pressure

56. Which of the following turbines is suitable for specific speed ranging from 300 to 1000 and heads below 30 m:

Correct : B. Kaplan

57. Specific speed of a turbo-machine

Correct : A. Relates the shape rather than the size of the machine

58. In an outward radial flow turbine energy conversion process is

Correct : D. None of the above.

59. Which of the following turbines is least efficient under part load conditions:

Correct : A. Propeller

60. A surge tank is used to

Correct : C. Relieve the pipeline of excessive pressure transients

61. Which of the following turbines is most efficient at partload operation?

Correct : A. Kaplan

62. With respect to a Kaplan turbine which of the following statements is incorrect?

Correct : B. It is designed for flow velocity of mixed flow type.

63. Specific speed of an impulse turbine (Pelton wheel) ranges from

Correct : A. 12 to 70

64. Cavitation damage in turbine runner occurs near the

Correct : B. Outlet on the convex side of blades

65. Which of the following serious problems arise from cavitation?

Correct : D. All of the above.

66. A Kaplan turbine is

Correct : B. Low head axial flow turbine

67. An impulse turbine requires

Correct : A. High head and small quantity of flow

68. ......of a turbine is defined as the ratio of power available at the turbine shaft to the power supplied by the water jet.

Correct : C. Overall efficiency

69. The ratio of power developed by the runner to the power supplied by the jet at entrance to the turbine is known as

Correct : A. Hydraulic efficiency

70. The water which acts on the runner blades of a reaction turbine is under a pressure

Correct : C. Above atmospheric

71. The runner passages of a reaction turbine are

Correct : B. Always completely filled with water

72. The value of speed ratio (Ku) in case of a Francis turbine ranges from

Correct : C. 0.6 to 0.9

73. The value of flow ratio (Kf) in case of a Francis turbine varies from:

Correct : B. 0.15 to 0.30

74. A Kaplan turbine claims which of the following advantages over a Francis turbine?

Correct : D. All of the above.

75. Which of the following draft tubes is suited particularly for helical flow?

Correct : C. Moody’s spreading draft tube.

76. Which of the following surge tank is also called a throttled surge tank?

Correct : C. Restricted orifice surge tank.

77. Which of the following types of impeller is used for centrifugal pumps dealing with muds?

Correct : D. Open.

78. Which of the following statements is correct with reference to an impeller with backward curved vanes?

Correct : A. It has a falling head - discharge characteristic.

79. The head developed by a centrifugal pump may be expressed as

Correct : B. H = Vw2 u2 /g

80. With reference to a centrifugal pump which of the following statements is incorrect?

Correct : D. The discharge control valve is fitted in the suction pipe.

81. A centrifugal pump should be so installed above the water level in the sump such that

Correct : B. The negative pressures do not reach as low a value as the vapour pressure

82. The specific speed of a pump is defined as the speed of unit of such a size that it

Correct : B. Delivers unit discharge at unit head

83. Which of the following statements pertaining to a given centrifugal pump is correct?

Correct : C. Discharge varies directly as speed

84. The delivery valve, while starting centrifugal pump, is kept

Correct : A. Fully closed

85. Which of the following is not a dimensionless parameter?

Correct : B. Specific speed

86. With reference to manometric head which of the following statements is correct?

Correct : D. It is the difference in the piezometric heads between the points on the delivery and suction pipes as close to the pump as possible.

87. Higher specific speeds (160 to 500) of centrifugal pump indicate that the pump is of

Correct : B. Axial flow type

88. What will happen if requirements of net positive suction head (NPSH) for a given pump are not satisfied?

Correct : A. The pump will get cavitated.

89. In centrifugal pumps, cavitation is reduced by

Correct : D. Reducing the suction head.

90. Which of the following statements pertaining to a centrifugal pump is incorrect?

Correct : A. The suction lift of a pump can be upto 10·3 m or even more.

91. Regarding cavitation which of the following statements in incorrect?

Correct : B. Thoma’s cavitation parameter has different expressions for turbines and pumps.

92. A centrifugal pump is taking much of power, the probable reason may be

Correct : A. Liquid being pumped is heavy

93. In rotodynamic pumps, the increase in energy level is due to

Correct : D. Combination of a, b and c.

94. In a pump there is

Correct : A. Accelerating flow

95. In a centrifugal pump the regulating valve is provided on

Correct : B. Delivery pipe

96. In a centrifugal pump the sum of suction head and delivery head is known as

Correct : C. Static head

97. Regarding manometric head (Hmano) which of the following relations is correct?

Correct : D. All of the above.

98. The ratio of power outlet of the pump to the power input to the pump is known as

Correct : B. Overall efficiency

99. The flow ratio in case of a centrifugal pump varies from

Correct : A. 0.1 to 0.25

100. ..... is a device which increases the intensity of pressure of a given liquid with the help of low pressure liquid of large quantity.

Correct : D. Hydraulic intensifier.