Fluid Mechanics Sheet 4

1) Question.

Size of venturimeter is specified by -
Answer.
- 1
  
  pipe diameter
- 2
  
  throat diameter
- 3
  
  angle of diverging section
- 4
  
  both pipe diameter as well as throat diameter
Answer: 4

Explanation:
2) Question.

The pitot static tube measures -
Answer.
- 1
  
  stagnation pressure
- 2
  
  static pressure
- 3
  
  dynamic pressure
- 4
  
  difference in total and dynamic pressure
Answer: 3

Explanation:
3) Question.

The theoritical value of coefficient of contraction of a sharp edged orifice is -
Answer.
- 1
  
  0.611
- 2
  
  0.85
- 3
  
  0.98
- 4
  
  1.00
Answer: 1

Explanation:
4) Question.

Hot wire anemometer is used to measure -
Answer.
- 1
  
  discharge
- 2
  
  velocity of gas
- 3
  
  pressure intensity of gas
- 4
  
  pressure intensity of liquid
Answer: 2

Explanation:
5) Question.

The pitot tube is used to measure -
Answer.
- 1
  
  velocity at stagnation point
- 2
  
  stagnation pressure
- 3
  
  static pressure
- 4
  
  dynamic pressure
Answer: 2

Explanation:
6) Question.

In steady flow of a fluid, the total acceleration of any fluid particle -
Answer.
- 1
  
  can be zero
- 2
  
  is never zero
- 3
  
  is always zero
- 4
  
  is independent of co-ordinates
Answer: 1

Explanation:
7) Question.

Equation of continuity is based on the principle of conservation of -
Answer.
- 1
  
  mass
- 2
  
  energy
- 3
  
  momentum
- 4
  
  none of the above
Answer: 1

Explanation:
8) Question.

Stream lines and path lines always coincide in case of -
Answer.
- 1
  
  steady flow
- 2
  
  laminar flow
- 3
  
  uniform flow
- 4
  
  turbulent flow
Answer: 1

Explanation:
9) Question.

In a forced vortex motion, the velocity of flow is -
Answer.
- 1
  
  directly proportional to its radial distance from axis of rotation
- 2
  
  inversely proportional to its radial distance from the axis of rotation
- 3
  
  inversely proportional to the square of its radial distance from the axis of rotation
- 4
  
  directly proportional to the square of its radial distance from the axis of rotation
Answer: 1

Explanation:
10) Question.

The motion of air mass in a tornado is a -
Answer.
- 1
  
  free vortex motion
- 2
  
  forced vortex motion
- 3
  
  free vortex at centre and forced vortex outside
- 4
  
  forced vortex at centre and free vortex outside
Answer: 4

Explanation:
11) Question.

The cavitation parameter is given by

[ p is the absolute pressure of the point of consideration, $p_{a}$ is atmosphere pressure, $p_{v}$ is vapour pressure of liquid, $ρ$ is the density of the liquid and V is the velocity]
Answer.
- 1
  
  $\frac{p - p_{v}}{0.5 ρ V^{2}}$
- 2
  
  $\frac{p_{v} - p}{0.5 ρ V^{2}}$
- 3
  
  $\frac{p_{a} - p}{0.5 ρ V^{2}}$
- 4
  
  $\frac{p - p_{a}}{0.5 ρ V^{2}}$
Answer: 1

Explanation:
12) Question.

Given that,

$S_{0}$ = slope of the channel bottom,

$S_{e}$ = slope of the energy line,

F= Froude number,

the equation of gradually varied flow is expressed as
Answer.
- 1
  
  $\frac{d y}{d x} = \frac{S_{0} - S_{e}}{1 + F^{2}}$
- 2
  
  $\frac{d y}{d x} = \frac{S_{0} - S_{e}}{1 - F^{2}}$
- 3
  
  $\frac{d y}{d x} = \frac{S_{0} + S_{e}}{1 + F^{2}}$
- 4
  
  $\frac{d y}{d x} = \frac{S_{0} + S_{e}}{1 - F^{2}}$
Answer: 2

Explanation:
13) Question.

A liquid of density $ρ$ and bulk modulus K flows with a mean velocity V in a long rigid pipe of diameter D. A sudden closure of a valve at the end of the pipe produces a maximum water hammer head $h_{w}$ , which is equal to
Answer.
- 1
  
  $\frac{V \sqrt{ρ}}{g \sqrt{K}}$
- 2
  
  $\frac{V \sqrt{K}}{g \sqrt{ρ}}$
- 3
  
  $\frac{V \sqrt{g}}{ρ \sqrt{K}}$
- 4
  
  $\frac{V ρ}{\sqrt{g K}}$
Answer: 2

Explanation:
14) Question.

For a circular channel (with $r_{0}$ as the radius of the channel) to be efficient,
Answer.
- 1
  
  the half subtended angle at the centre with respect to the water level must be $151^{\circ} 10'$
- 2
  
  depth of flow must be $1.88 r_{0}$
- 3
  
  depth of maximum velocity must be $1.62 r_{0}$
- 4
  
  the half subtended angle at the centre with respect to the water level must be $90^{0}$
Answer: 3

Explanation:
15) Question.

The loss of energy in a hydraulic jump formed in a rectangular channel is given by (Symbols have the usual meanings)
Answer.
- 1
  
  $∆ E = \frac{{(y_{2} - y_{1})}^{3}}{4 y_{1} y_{2}}$
- 2
  
  $∆ E = \frac{v Q {(y_{2} - y_{1})}^{3}}{8 y_{1} y_{2}}$
- 3
  
  $∆ E = \frac{v Q {(y_{2} - y_{1})}^{3}}{75 x 4 y_{1} y_{2}} - H P$
- 4
  
  $∆ E = \frac{{(y_{1} - y_{2})}^{3}}{4 y_{1} y_{2}}$
Answer: 1

Explanation:
16) Question.

The condition for complete similarity to exist between model and prototype, where both gravity and viscous forces are important, is

[ $μ_{r}$ = kinematic viscosity ratio and $L_{r}$ = length scale ratio]
Answer.
- 1
  
  $μ_{r =} {L_{r}}^{3 / 2}$
- 2
  
  $μ_{r} = {L_{r}}^{5 / 2}$
- 3
  
  $μ_{r} = {L_{r}}^{1 / 2}$
- 4
  
  $μ_{r} = {L_{r}}^{2 / 3}$
Answer: 1

Explanation:
17) Question.

Which of the following could be a $π$ -parameter of the function $ϕ$ (F, V, $ρ, μ,$ L)=0 when V, $ρ$ and L are taken as repeating variables ?
Answer.
- 1
  
  $\frac{V L μ^{2}}{ρ}$
- 2
  
  $\frac{F^{2}}{V^{2} ρ L}$
- 3
  
  $\frac{F}{ρ L^{2} V^{2}}$
- 4
  
  $\frac{V L ρ}{\sqrt{μ}}$
Answer: 3

Explanation:
18) Question.

A dimensionless combination of surface tension $σ$ , density $ρ$ , diameter D and velocity V is
Answer.
- 1
  
  $σ D / ρ V$
- 2
  
  $σ D^{2} / ρ V$
- 3
  
  $σ / ρ V^{2} D$
- 4
  
  $σ D / ρ V^{2}$
Answer: 3

Explanation:
19) Question.

Which one of the following velocity fields represents a possible fluid now ?
Answer.
- 1
  
  u=x ; v=y
- 2
  
  $u = x^{2}; v = y^{2}$
- 3
  
  $u = x y; v = x^{2} y^{2}$
- 4
  
  u=x ; v= -y
Answer: 4

Explanation:
20) Question.

The mean velocities at two ends of a stream tube 10 cm apart are 2.5 m/s and 3 m/s. The convectional tangential acceleration mid-way is
Answer.
- 1
  
  zero
- 2
  
  $0.5 m / s^{2}$
- 3
  
  $13.75 m / s^{2}$
- 4
  
  non determinable
Answer: 3

Explanation:

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