Fluid Mechanics Sheet 15

1) Question.

If the elevation of hydraulic grade line at the junction of three pipes is above the elevation of reservoirs B and C and below resoivoir A, then the direction of flow will be -
Answer.
- 1
  
  from reservoir A to reservoirs B and C
- 2
  
  from reservoir B to reservoirs C and A
- 3
  
  from reservoir C to reservoirs A and B
- 4
  
  unpredictable
Answer: 1

Explanation:
2) Question.

When time of closure $t_{c} = L / v_{0}$ (where L is the length of pipe and $v_{0}$ is speed of pressure wave), the portion of pipe length subjected to maximum head is -
Answer.
- 1
  
  L/4
- 2
  
  L/3
- 3
  
  L/2
- 4
  
  L
Answer: 3

Explanation:
3) Question.

If a sphere of diameter 1 cm falls in castor oil of kinematic viscosity 10 stokes, with a terminal velocity of 1.5 cm/sec, the coefficient of drag on the sphere is -
Answer.
- 1
  
  less than 1
- 2
  
  between 1 and 100
- 3
  
  160
- 4
  
  200
Answer: 3

Explanation:
4) Question.

If x is the distance from leading edge, then the boundary layer thickness in laminar flow varies as -
Answer.
- 1
  
  $x^{1 / 2}$
- 2
  
  $x^{4 / 5}$
- 3
  
  $x^{3 / 5}$
- 4
  
  $x^{1 / 7}$
Answer: 1

Explanation:
5) Question.

For a sphere of radius 15 cm moving with a uniform velocity of 2 m/sec through a liquid of specific gravity 0.9 and dynamic viscosity 0.8 poise, the Reynolds number will be -
Answer.
- 1
  
  300
- 2
  
  337.5
- 3
  
  600
- 4
  
  675
Answer: 4

Explanation:
6) Question.

Which of the following is an incorrect statement ?
Answer.
- 1
  
  Coefficient of contraction of a venturimeter is unity.
- 2
  
  Flow nozzle is cheaper than venturimeter but has higher energy loss.
- 3
  
  Discharge is independent of orientation of venturimeter whether it is horizontal, vertical or inclined.
- 4
  
  None of the above statement is correct.
Answer: 4

Explanation:
7) Question.

A fluid jet discharging from a 4 cm diameter orifice has a diameter 3 cm at its vena contracta. If the coefficient of velocity is 0.98, the coefficient of discharge for the orifice will be -
Answer.
- 1
  
  $0.98 \times {(0.75)}^{2}$
- 2
  
  $\frac{{(0.75)}^{2}}{0.98}$
- 3
  
  $0.98 \times {(1.33)}^{2}$
- 4
  
  $\frac{0.98}{{(1.33)}^{2}}$
Answer: 1

Explanation:
8) Question.

Which of the following is used to measure the discharge ?
Answer.
- 1
  
  current meter
- 2
  
  venturimeter
- 3
  
  pitot tube
- 4
  
  hotwire anemometer
Answer: 2

Explanation:
9) Question.

If velocity is zero over 1/3rd of a cross-section and is uniform over remaining 2/3rd of the cross-section, then the ocrrection factor for kinetic energy is -
Answer.
- 1
  
  4/3
- 2
  
  3/2
- 3
  
  9/4
- 4
  
  27/8
Answer: 1

Explanation:

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