Fluid Mechanics MCQs

Question 1

Disc compensators are provided in large diameter fuel gas carrying pipelines to

Accepted Answer

Account for contraction/expansion of pipe due to temperature changes of the surroundings

Answer

Keep the pipe in proper orientation

Answer

Make the pipe joint leak-proof

Answer

Account for the pressure variation side the pipeline

Question 2

During ageing of fluid carrying pipes, the

Accepted Answer

Absolute roughness increases linearly with time

Answer

Pipe becomes smoother with use

Answer

Friction factor increases linearly with time

Answer

Absolute roughness decreases with time

Question 3

A gas (density = 1.5 kg/m3, viscosity = 2 × 10-5 kg/m.s) flowing through a packed bed (particle size = 0.5 cm, porosity = 0.5) at a superficial velocity of 2 m/s causes a pressure drop of 8400 Pa/m. The pressure drop for another gas, with density of 1.5 kg/m3 and viscosity of 3 × 10-5 kg/m.s flowing at 3 m/s will be

Accepted Answer

12600 Pa/m

Answer

8400 Pa/m

Answer

18900 Pa/m

Answer

16800 Pa/m

Question 4

Centrifugal pump can't be used to pump

Accepted Answer

Thick molten soap at 80°C

Answer

Molten sodium (used as a coolant in Fast Breeder Reactor)

Answer

Moderately viscous vegetable oil used in soap industry

Answer

None of the above

Question 5

The general relationship between speed N, head H, power P and discharge Q for a centrifugal pump is

Accepted Answer

Q ∝ N : H ∝ N2 : P ∝ N3

Answer

Q ∝ N2 : H ∝ N3 : P ∝ N

Answer

Q ∝ N : H ∝ N3 : P ∝ N2

Answer

Q ∝ N3 : H ∝ N : P ∝ N2

Question 6

The percentage slip in a reciprocating pump set is given by the % of (where, Q1 = actual discharge Q2 = theoretical discharge)

Accepted Answer

$$\frac{{{{	ext{Q}}_2} - {{	ext{Q}}_1}}}{{{{	ext{Q}}_2}}}$$

Answer

$$\frac{{{{	ext{Q}}_1}}}{{{{	ext{Q}}_2}}}$$

Answer

$$\frac{{{{	ext{Q}}_2}}}{{{{	ext{Q}}_1}}}$$

Answer

$$\frac{{{{	ext{Q}}_2} - {{	ext{Q}}_1}}}{{{{	ext{Q}}_1}}}$$

Question 7

What is the shear rate at the pipe wall, in case of laminar flow of Newtonion fluids in a pipe of diameter 'D' & length 'L' incurring a pressure drop 'Δp' with average velocity 'Vavg'?

Accepted Answer

8 . Vavg/D

Answer

D Δp/8L

Answer

D Δp/4L

Answer

4 . Vavg/D

Question 8

Gear pump

Accepted Answer

Is a positive displacement pump

Answer

Is a centrifugal pump

Answer

Is a non-positive displacement pump

Answer

Can be started with delivery valve closed

Question 9

The discharge through a venturimeter depends upon

Accepted Answer

Pressure drop only

Answer

Its orientation

Answer

Co-efficient of contraction only

Answer

None of these