Laminar and Turbulent Flows: Master Fluid Mechanics Concepts

Question 1

In turbulent flow, the fluid velocity:

Accepted Answer

Fluctuates randomly, resulting in unpredictable flow patterns.

Answer

Is constant in both magnitude and direction.

Answer

Follows a parabolic profile, with the highest velocity at the center of the flow.

Answer

Is always laminar and can be predicted using analytical methods.

Question 2

The Reynolds number is a dimensionless parameter that primarily indicates:

Accepted Answer

The ratio of fluid inertia to viscous forces.

Answer

The ratio of fluid density to viscosity.

Answer

The ratio of pressure forces to gravitational forces.

Answer

The ratio of surface tension forces to cohesive forces.

Question 3

In a turbulent boundary layer, which of the following occurs?

Accepted Answer

Fluid velocity fluctuates rapidly, resulting in a highly irregular flow pattern near the surface.

Answer

Shear stresses are predominantly laminar, with smooth fluid flow near the surface.

Answer

Energy dissipation is minimal, leading to efficient flow conditions.

Answer

The flow is fully developed, with no further changes in velocity or turbulence intensity.

Question 4

The friction factor in turbulent pipe flow is primarily influenced by which factor?

Accepted Answer

Reynolds number and pipe roughness

Answer

Fluid viscosity and temperature

Answer

Pipe diameter and length

Answer

Gravitational forces and buoyancy effects

Question 5

Which of the following is NOT a potential consequence of turbulence?

Accepted Answer

Lower energy consumption and reduced operating costs

Answer

Increased drag and heat transfer

Answer

Reduced flow stability and predictability

Answer

Enhanced fluid mixing and mass transfer

Question 6

Within which range of Reynolds numbers is turbulent flow typically observed?

Accepted Answer

Re > 4000

Answer

Re < 2000

Answer

2000 < Re < 4000

Answer

Re < 1000

Question 7

Which of the following factors does NOT influence the transition from laminar to turbulent flow?

Accepted Answer

Fluid acceleration

Answer

Fluid viscosity

Answer

Pipe diameter

Answer

Surface roughness

Question 8

In fully developed laminar flow, the velocity profile is:

Accepted Answer

Parabolic

Answer

Linear

Answer

Exponential

Answer

Hyperbolic

Question 9

How does the friction factor vary in relation to Reynolds number in turbulent flow?

Accepted Answer

Increases then decreases with Re

Answer

Increases linearly with Re

Answer

Decreases linearly with Re

Answer

Remains constant with Re

Question 10

The Reynolds number is a dimensionless quantity used to characterize:

Accepted Answer

Flow regime

Answer

Fluid viscosity

Answer

Pipe diameter

Question 11

In pipe flow, which parameter primarily influences the transition from laminar to turbulent flow?

Accepted Answer

Pipe diameter

Answer

Pipe roughness

Answer

Fluid temperature

Question 12

Which factor contributes to the destabilization of laminar flow?

Accepted Answer

Surface roughness

Answer

High fluid density

Answer

Low flow velocity

Question 13

The Darcy-Weisbach equation can be used to calculate the:

Accepted Answer

Pressure drop in a pipe

Answer

Flow rate in a channel

Answer

Velocity profile in a boundary layer

Question 14

To visualize the intricate flow patterns in turbulent flows, which experimental technique is most effective?

Accepted Answer

Particle image velocimetry (PIV)

Answer

Hot-wire anemometry

Answer

Laser Doppler velocimetry (LDV)

Answer

Flow visualization using dyes

Question 15

Which factors primarily cause flow separation in turbulent boundary layers, and how do they affect drag and heat transfer rates?

Accepted Answer

Adverse pressure gradient and large-scale coherent structures

Answer

High surface roughness and low Reynolds number

Answer

Low surface temperature and high fluid viscosity

Answer

Sudden expansion of the flow channel and compliant boundary conditions

Question 16

Which of the following is a defining characteristic of laminar flow?

Accepted Answer

Smooth, predictable motion with a parabolic velocity profile

Answer

High drag and shear stress

Answer

Non-uniform temperature distribution

Answer

Formation of irregular, unpredictable eddies

Question 17

What dimensionless number is used as the primary criterion to determine the transition between laminar and turbulent flow?

Accepted Answer

Reynolds number (Re)

Answer

Froude number (Fr)

Answer

Nusselt number (Nu)

Answer

Weber number (We)

Question 18

Which of the following is a consequence of turbulence on fluid flow?

Accepted Answer

Increased drag, mixing, and heat transfer

Answer

Laminar boundary layer formation

Answer

Reduced pressure drop

Answer

Smooth, streamlined flow

Question 19

What is the key distinction between the velocity profiles in laminar and turbulent flow in a circular pipe?

Accepted Answer

Laminar flow: parabolic profile, Turbulent flow: flatter, more uniform profile

Answer

Laminar flow: uniform profile, Turbulent flow: parabolic profile

Answer

Laminar flow: turbulent core, Turbulent flow: laminar boundary layer

Question 20

Which of the following statements about turbulent flow is accurate?

Accepted Answer

It is characterized by random, swirling eddies and increased momentum exchange

Answer

It occurs only in highly viscous fluids

Answer

It cannot exist within boundary layers

Answer

It is always more efficient than laminar flow

Question 21

Which device is commonly used to accurately measure the velocity of turbulent flow?

Accepted Answer

Laser Doppler anemometer (LDA)

Answer

Pitot tube

Answer

Orifice plate

Answer

Venturi meter

Question 22

What is the primary purpose of using flow straighteners in turbulent flow measurements?

Accepted Answer

To remove swirling eddies and ensure a more uniform flow profile

Answer

To reduce pressure drop

Answer

To increase turbulence intensity

Answer

To directly measure flow rate

Question 23

Which factor can lead to premature transition from laminar to turbulent flow?

Accepted Answer

Surface roughness

Answer

High fluid viscosity

Answer

Large pipe diameter

Answer

Low flow velocity

Question 24

What is a fundamental challenge in modelling turbulent flow?

Accepted Answer

Its inherent randomness and complexity make it difficult to describe mathematically

Answer

Uncertainties in boundary conditions

Answer

Computational limitations in solving complex equations

Answer

Lack of experimental data for validation