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Fluid Mechanics and Machines & Hydrology PYQ – TN TRB Lecturer

      

31. The basic assumptions of unit hydrograph theory are _____ .

[TN TRB 2021: 1 Mark]

  1. Non linear response
  2. Time invariance and linear response
  3. Linear response and linear time variance
  4. Non linear time variance and linear response
Answer: Option B
Explanation:
The basic assumptions of unit hydrograph theory are

  • Time invariance – Unit hydrograph for a given effective rainfall in a catchment is not time dependent.
  • Linear response – The direct runoff response to rainfall excess is assumed to be linear.

32. An ideal fluid is _____ .

[TN TRB 2021: 1 Mark]

  1. Highly viscous
  2. Frictionless and compressible
  3. One which obeys Newton’s law of viscosity
  4. One which is incompressible and has zero viscosity
Answer: Option D
Explanation:
An ideal fluid is the one which is incompressible and non-viscous.

33.  The printer’s ink is an example of _____ .

[TN TRB 2021: 1 Mark]

  1. Newtonian fluid
  2. Non-Newtonian fluid
  3. Thyxotropic substance
  4. Elastic solid
Answer: Option C
Explanation:
Thyxotropic fluid is a type of non-Newtonian fluid. Examples of thyxotropic fluid are printer’s ink, enamels.

34.  _____ is the ratio of Inertia force to the viscous force.

[TN TRB 2021: 1 Mark]

  1. Froude’s number
  2. Reynolds number
  3. Mach number
  4. Euler number
Answer: Option B
Explanation:

Reynold’s number =

Inertia force

Viscous force

35.  Darcy-Weisbach equation is used to determine the loss of head due to _____ .

[TN TRB 2021: 1 Mark]

  1. Friction
  2. Sudden enlargement
  3. Sudden contraction
  4. Obstruction
Answer: Option A
Explanation:
Darcy-Weishbach equation is used to determine the major head loss due to friction.

hL =

fLv2

2gD


Where,
f – friction factor
L – length of flow considered
v – Average velocity of flow
g – Acceleration due to gravity
D – Diameter of pipe

36.  For maximum efficiency of a series of curved vanes, its velocity is _____ .

[TN TRB 2021: 1 Mark]

  1. Equal to velocity of jet
  2. ¾ of velocity of jet
  3. ½ of velocity of jet
  4. â…“ of velocity of jet
Answer: Option C
Explanation:
Let,
m – mass flow rate,
u – velocity of curved vanes,
v – velocity of jet
Efficiency of a series of curved vanes,

η =

Work done per sec

Kinetic energy of the jet

=

m (v-u) x u

½ mv2

⇒ η =

2u (v-u)

v2

For maximum efficiency ,

∂η

∂u

= 0

⇒

∂{

2u (v-u)

v2

}



∂u

= 0

⇒ v – 2u = 0
⇒ u = v/2
Thus for maximum efficiency, velocity of curved vane must be 0.5 times the velocity of the jet.

37.  The specific speed of a pump is expressed as _____ .

[TN TRB 2021: 1 Mark]

  1. N√  Q  H
  2. N√  Q  H2
  3. N√  Q  H3/4
  4. N√  Q  H5/4
Answer: Option C
Explanation:
Specific speed of a pump is the speed of a symmetrical pump such that it will deliver unit discharge when operated under unit head.
The formula to calculate the specific speed of pump (Ns) is,

Ns =

N√  Q 


H3/4


38.  The boundary layer exists due to _____  .

[TN TRB 2021: 1 Mark]

  1. Surface tension
  2. Gravitational effect
  3. Viscosity of fluid
  4. Pressure
Answer: Option C
Explanation:

39.  The most essential condition for formation of hydraulic jump is _____ .

[TN TRB 2021: 1 Mark]

  1. The constant specific energy
  2. The existence of supercritical flow before the jump
  3. The existence of subcritical flow before the jump
  4. The existence of critical flow before the jump
Answer: Option B
Explanation:
Hydraulic jump occurs when the depth of flow of water changes from supercritical to subcritical state i.e., supercritical flow exists before the jump.

40.  Which of the following is used for both velocity control device and flow control device ?

[TN TRB 2021: 1 Mark]

  1. Proportional flow weir
  2. Parshall flume
  3. Venturi meter
  4. Orifice meter
Answer: Option B
Explanation:

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