Fluid Mechanics Sheet 3

1) Question.

If the velocity is zero over half of the cross-sectional area and is uniform over the remaining half, then the momentum correction factor is -
Answer.
- 1
  
  1
- 2
  
  4/3
- 3
  
  2
- 4
  
  4
Answer: 3

Explanation:
2) Question.

When the velocity distribution is uniform over the cross-section, the correction factor for momentum is -
Answer.
- 1
  
  0
- 2
  
  1
- 3
  
  4/3
- 4
  
  2
Answer: 2

Explanation:
3) Question.

The equation $\frac{p}{w} + \frac{v^{2}}{2 g} + z =$ constant is based on the following assumptions regarding the flow of fluid :
Answer.
- 1
  
  steady, frictionless, incompressible and along a streamline
- 2
  
  steady, frictionless, uniform and along a streamline
- 3
  
  steady, incompressible, uniform and along a streamline
- 4
  
  steady, frictionless, incompressible and uniform
Answer: 1

Explanation:
4) Question.

The eddy viscosity for turbulent flow is -
Answer.
- 1
  
  a function of temperature only
- 2
  
  a physical property of the fluid
- 3
  
  dependent on the flow
- 4
  
  independent of the flow
Answer: 3

Explanation:
5) Question.

The horizontal component of force on a curved surface is equal to the -
Answer.
- 1
  
  product of pressure intensity at its centroid and area
- 2
  
  force on a vertical projection of the curved surface
- 3
  
  weight of liquid vertically above the curved surface
- 4
  
  force on the horixontal projection of the curved surface
Answer: 2

Explanation:
6) Question.

A right circular cylinder open at the top is filled with liquid and rotated about its vertical axis at such a speed that half the liquid spills out, then the pressure intensity at the centre of bottom is -
Answer.
- 1
  
  zero
- 2
  
  one-fourth its value when cylinder was full
- 3
  
  one half its value when cylinder was full
- 4
  
  cannot be predicted from the given data
Answer: 1

Explanation:
7) Question.

An open cubical tank of 2 m side is filled with water. If the tank is rotated with an acceleration such that half of the water spills out, then the acceleration is equal to -
Answer.
- 1
  
  g/3
- 2
  
  g/2
- 3
  
  2g/3
- 4
  
  g
Answer: 4

Explanation:
8) Question.

When a liquid rotates at a constant angular velocity about a vertical axis as a rigid body, the pressure intensity varies -
Answer.
- 1
  
  linearly with radial distance
- 2
  
  as the square of the radial distance
- 3
  
  inversely as the square of the radial distance
- 4
  
  inversely as the radial distance
Answer: 2

Explanation:
9) Question.

If a vessel containing liquid moves downward with a constant accelaration equal to 'g', then -
Answer.
- 1
  
  the pressure throughout the liquid mass is atmospheric
- 2
  
  there will be vacuum in the liquid
- 3
  
  the pressure in the liquid mass is greater than hydrostatic pressure
- 4
  
  none of the above
Answer: 1

Explanation:
10) Question.

A vertical rectangular plane surface is submerged in water such that its top and bottom surfaces are 1.5 m and 6.0 m respectively below the free surface. The position of centre of pressure below the free surface will be at a distance of -
Answer.
- 1
  
  3.75 m
- 2
  
  4.0 m
- 3
  
  4.2 m
- 4
  
  4.5 m
Answer: 3

Explanation:
11) Question.

For a given specific energy E, the critical depth $y_{c}$ for a rectangular channel is given by
Answer.
- 1
  
  $y_{c} = \frac{3}{2} E$
- 2
  
  $y_{c} = \frac{2}{3} E$
- 3
  
  $y_{c} = \frac{4}{5} E$
- 4
  
  $y_{c} = \frac{3}{4} E$
Answer: 2

Explanation:
12) Question.

The critical depth of flow in a most economical triangular channel section for a discharge of $1 m^{3} / s e c$ is given by
Answer.
- 1
  
  ${(\frac{1}{9.8})}^{1 / 5}$ metre
- 2
  
  ${(\frac{1}{9.8})}^{1 / 3}$ metre
- 3
  
  ${(\frac{1}{4.9})}^{1 /} 5$ metre
- 4
  
  ${(\frac{1}{4.9})}^{1 /} 3$ metre
Answer: 3

Explanation:
13) Question.

The loss of energy due to sudden enlargement is given by

[ $A_{1,} v_{1}$ are area of cross-section and velocity at entry and $A_{2,} v_{2}$ are area of cross-section and velocity at exit]
Answer.
- 1
  
  $\frac{{v_{2}}^{2}}{2 g} {(\frac{A_{2}}{A_{1}} - 1)}^{2}$
- 2
  
  ${(\frac{v_{1} - v_{2}}{2 g})}^{2}$
- 3
  
  $\frac{{v_{1}}^{2} - {v_{2}}^{2}}{2 g}$
- 4
  
  $\frac{{v_{1}}^{2}}{2 g} {(1 - \frac{A_{2}}{A_{1}})}^{2}$
Answer: 1

Explanation:
14) Question.

If the velocity, bulk modulus of elasticity and the mass density of a fluid are denoted by U, K and $ρ$ respectively, then the Mach number is given by
Answer.
- 1
  
  $\frac{U \sqrt{K}}{\sqrt{ρ}}$
- 2
  
  $\frac{U \sqrt{ρ}}{\sqrt{K}}$
- 3
  
  $\frac{ρ \sqrt{U}}{\sqrt{K}}$
- 4
  
  $\frac{K \sqrt{U}}{\sqrt{ρ}}$
Answer: 2

Explanation:
15) Question.

Streamlines and equipotential lines
Answer.
- 1
  
  can be drawn graphically for viscous flow around any boundary
- 2
  
  form meshes of perfect squares
- 3
  
  are orthogonal wherever they meet
- 4
  
  can be determined mathematically for all boundary conditions
Answer: 3

Explanation:
16) Question.

A penstock is 2000 m long and the velocity of pressure wave in it is 1000 m/s. Water hammer pressure head for instantaneus closure of value at the downstream end of pipe is 60 m. If the valve is closed in 4 secs, then the peak water hammer pressure head is equal to
Answer.
- 1
  
  15 m
- 2
  
  30 m
- 3
  
  60 m
- 4
  
  120 m
Answer: 3

Explanation:

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