Viscous Flows: Master Fluid Dynamics for Engineering Applications

Question 1

In boundary layer theory, which parameter defines the thickness of the boundary layer?

Accepted Answer

Distance from the surface where velocity reaches 99% of the free-stream velocity

Answer

Location where velocity gradient is zero

Answer

Point where shear stress is zero

Answer

Constant value independent of flow velocity

Question 2

In viscous flows, what characterizes the boundary layer?

Accepted Answer

A thin region near the solid surface with significant velocity gradients

Answer

Increasing thickness in the flow direction

Answer

Exclusively laminar flow

Answer

No impact on the overall drag force

Question 3

Which of the following is true for turbulent pipe flow compared to laminar pipe flow?

Accepted Answer

Velocity profile is flatter and less skewed

Accepted Answer

Flow is more sensitive to surface roughness

Answer

Pressure drop is lower over a given pipe length

Answer

Fluid particles move in straight lines parallel to the pipe axis

Question 4

In the context of viscous fluid dynamics, which of the following flow regimes is NOT characterized by viscous effects?

Accepted Answer

Supercritical flow

Answer

Laminar flow

Answer

Turbulent flow

Answer

Creeping flow

Question 5

Which type of fluid is NOT defined by its viscosity?

Accepted Answer

Ideal fluid

Answer

Newtonian fluid

Answer

Pseudoplastic fluid

Answer

Dilatant fluid

Question 6

Which statement best describes the defining characteristic of viscous flows?

Accepted Answer

Frictional forces between fluid layers

Answer

Exclusively laminar flow

Answer

Constant viscosity

Answer

Inherent incompressibility

Question 7

What is the definition of viscosity in viscous fluids?

Accepted Answer

Viscosity is the resistance to flow due to internal friction.

Answer

Viscosity is a measure of fluid thickness.

Answer

Viscosity only applies to very viscous fluids.

Answer

Viscosity has no effect on fluid flow patterns.

Question 8

In a Newtonian fluid, shear stress is directly proportional to what?

Accepted Answer

Velocity gradient

Answer

Square of the velocity gradient

Answer

Inverse of the velocity gradient

Answer

Independent of the velocity gradient

Question 9

Which of the following is NOT a type of non-Newtonian fluid?

Accepted Answer

Ideal fluid

Answer

Bingham plastic

Answer

Dilatant fluid

Answer

Pseudoplastic fluid

Question 10

The Reynolds number is a dimensionless quantity that characterizes the flow regime of a fluid. Which of the following statements accurately describes the Reynolds number?

Accepted Answer

It represents the ratio of inertial forces to viscous forces acting on the fluid.

Answer

It represents the ratio of viscous forces to inertial forces acting on the fluid.

Answer

It represents the ratio of the fluid's density to its viscosity.

Answer

It represents the ratio of the fluid's velocity to its viscosity.

Question 11

Which fluid exhibits Newtonian behavior?

Accepted Answer

Newtonian

Answer

Bingham Plastic

Answer

Pseudoplastic

Answer

Dilatant

Question 12

Which property is NOT characteristic of Newtonian fluids?

Accepted Answer

Viscosity increases with increasing pressure

Answer

Constant viscosity at a given temperature

Answer

Linear relationship between shear stress and shear rate

Answer

Parabolic velocity profile in laminar pipe flow

Question 13

Which of the following is NOT a type of non-Newtonian fluid?

Accepted Answer

Newtonian fluid

Answer

Bingham plastic

Answer

Pseudoplastic

Answer

Dilatant

Question 14

Which of the following is NOT a type of non-Newtonian fluid?

Accepted Answer

Ideal Fluid

Answer

Bingham Plastic

Answer

Shear-thickening fluid

Answer

Pseudoplastic

Question 15

Which of the following is NOT a type of viscosity?

Accepted Answer

Bulk viscosity

Answer

Dynamic viscosity

Answer

Kinematic viscosity

Answer

Apparent viscosity

Question 16

Within the context of viscous flows, which flow regime marks the initial emergence of separation, transition, and turbulence?

Accepted Answer

Transitional regime

Answer

Stokes regime

Answer

Laminar regime

Question 17

For non-spherical particles in viscous flows, the drag force is best described by which relationship with velocity?

Accepted Answer

Drag force is proportional to a power of velocity, dependent on particle shape.

Answer

Drag force is proportional to velocity.

Answer

Drag force is proportional to the square of velocity.

Answer

Drag force is independent of velocity.

Question 18

Which property is NOT characteristic of Newtonian fluids?

Accepted Answer

Yield stress

Answer

Constant viscosity

Answer

Linear relationship between shear stress and shear rate

Answer

Time-independent viscosity

Question 19

In boundary layer theory, the Blasius solution approximates the velocity profile in a laminar boundary layer. Which assumptions are inherent in the Blasius solution?

Accepted Answer

The boundary layer is thin compared to the body's characteristic length.

Accepted Answer

The pressure gradient along the boundary layer is negligible.

Answer

The fluid is incompressible, inviscid, and irrotational.

Question 20

Identify the Newtonian fluid from the following options:

Accepted Answer

Newtonian fluid

Answer

Dilatant fluid

Answer

Bingham plastic

Answer

Pseudoplastic fluid

Question 21

What characteristic defines a Newtonian fluid?

Accepted Answer

Shear stress is directly proportional to shear rate.

Answer

Viscosity remains constant regardless of temperature.

Answer

The fluid has a yield stress.

Question 22

Which property is NOT characteristic of Newtonian fluids?

Accepted Answer

Viscosity is independent of pressure.

Answer

Viscosity is constant.

Answer

Shear stress is proportional to shear rate.

Answer

Exhibit laminar flow at low Reynolds numbers.

Question 23

In laminar flow between parallel plates, the velocity profile is parabolic. Which expression accurately describes the shear stress distribution?

Accepted Answer

Parabolic distribution from the upper plate to the lower plate

Answer

Linear decrease from the upper plate to the lower plate

Answer

Uniform distribution across the channel

Answer

Exponential decrease from the upper plate to the lower plate

Question 24

Identify the limitations of current theoretical models for predicting drag force on bluff bodies in viscous flows and suggest potential improvements.

Accepted Answer

Considering the effects of boundary layer separation and wake formation can improve the accuracy of drag predictions.

Answer

Existing models are generally accurate for all bluff body shapes and Reynolds numbers.

Answer

Computational fluid dynamics (CFD) can always provide accurate drag predictions for bluff bodies, regardless of their shape or flow conditions.

Answer

Drag predictions for bluff bodies are solely dependent on the fluid viscosity and velocity.

Question 25

In polymer processing, why is viscoelasticity important? How does it affect extrusion and molding techniques?

Accepted Answer

Viscoelasticity enhances mixing and heat transfer in molding processes, improving product quality and efficiency.

Accepted Answer

Polymer solutions' viscoelastic properties can be adjusted to optimize their flow behavior for specific processing needs.

Answer

Viscoelasticity is irrelevant in polymer processing because it only affects dilute solutions.

Answer

Viscoelasticity can be ignored in extrusion processes due to the relatively low shear rates involved.

Question 26

How does free-stream turbulence affect the transition of a boundary layer from laminar to turbulent flow?

Accepted Answer

Promotes earlier transition by amplifying Tollmien-Schlichting waves

Answer

Stabilizes laminar flow by suppressing disturbances

Answer

Delays transition by increasing the critical Reynolds number

Answer

Has no influence on boundary layer transition

Question 27

In a boundary layer, the greatest velocity gradient occurs in the:

Accepted Answer

Laminar sublayer

Answer

Transition layer

Answer

Turbulent sublayer

Answer

Fully developed layer

Question 28

Which dimensionless parameter quantifies the relative dominance of viscous forces compared to inertial forces in fluid flow?

Accepted Answer

Reynolds number

Answer

Mach number

Answer

Grashof number

Answer

Prandtl number

Question 29

What type of flow is characterized by smooth, organized layers and occurs when fluid velocity falls below a critical value?

Accepted Answer

Laminar flow

Answer

Turbulent flow

Answer

Boundary layer flow

Answer

Couette flow

Question 30

The Navier-Stokes equations are a system of:

Accepted Answer

Partial differential equations

Answer

Differential equations

Answer

Algebraic equations

Answer

Integral equations

Question 31

In a Couette flow, the fluid velocity:

Accepted Answer

Varies linearly with distance from the boundaries

Answer

Is zero at both boundaries

Answer

Is constant throughout the flow

Answer

Varies exponentially with distance from the boundaries

Question 32

Which fluid is an example of a non-Newtonian fluid?

Accepted Answer

Honey

Answer

Water

Answer

Air

Answer

Mercury

Question 33

The boundary layer thickness is typically defined as the distance from the surface where the:

Accepted Answer

Velocity reaches 99% of the freestream velocity

Answer

Velocity reaches 95% of the freestream velocity

Answer

Velocity reaches 90% of the freestream velocity

Answer

Velocity reaches 80% of the freestream velocity

Question 34

How does surface roughness affect boundary layer development and drag forces?

Accepted Answer

Increased surface roughness promotes a thicker boundary layer and increased drag forces.

Answer

Increased surface roughness leads to a thinner boundary layer and decreased drag forces.

Answer

Surface roughness has minimal effect on boundary layer thickness or drag forces.

Answer

Increased surface roughness results in a thinner boundary layer and increased drag forces.

Question 35

In viscous flow, shear stress is directly proportional to:

Accepted Answer

Velocity gradient

Answer

Pressure gradient

Answer

Kinematic viscosity

Answer

Fluid density

Question 36

The Reynolds number, a dimensionless parameter, characterizes the flow regime as:

Accepted Answer

Laminar or turbulent

Answer

Viscous or inviscid

Answer

Steady or unsteady

Answer

Compressible or incompressible

Question 37

In a hydrodynamic journal bearing, the fluid layer separating rotating and stationary surfaces is typically assumed to behave as:

Accepted Answer

A Newtonian fluid with constant viscosity

Answer

A power-law fluid exhibiting shear-thinning behavior

Answer

A Herschel-Bulkley fluid with a yield stress

Answer

A Bingham plastic fluid exhibiting both yield stress and shear-thinning behavior

Question 38

Boundary layer thickening downstream is primarily due to:

Accepted Answer

Momentum diffusion

Answer

Energy diffusion

Answer

Mass diffusion

Answer

Pressure diffusion

Question 39

The hydrodynamic lift force generated by a viscous fluid flowing over a curved surface is known as the:

Accepted Answer

Magnus effect

Answer

Bernoulli effect

Answer

Coanda effect

Answer

Venturi effect

Question 40

Question:
Identify the limitations of the lubrication approximation and explain when it is appropriate to use it in analyzing viscous flows.

Accepted Answer

The lubrication approximation is limited to thin fluid films with negligible pressure gradients across the film.

Accepted Answer

The lubrication approximation disregards inertial effects, assuming that viscous forces are dominant.

Answer

The lubrication approximation can be applied to all viscous flows, regardless of fluid properties or flow conditions.

Answer

It is always appropriate to use the lubrication approximation when analyzing viscous flows.

Question 41

The Reynolds number is a dimensionless parameter used to characterize the:

Accepted Answer

Relative significance of inertial forces to viscous forces

Answer

Relative significance of pressure forces to inertial forces

Answer

Relative significance of viscous forces to pressure forces

Answer

Relative significance of surface tension forces to pressure forces

Question 42

In a boundary layer flow, the shear stress at the surface is:

Accepted Answer

Maximum

Answer

Zero

Answer

Minimum

Answer

Equal to the free-stream velocity

Question 43

Which of the following is an example of laminar flow?

Accepted Answer

Flow in a pipe at low velocity and small diameter

Answer

Flow around an airplane wing at supersonic speeds

Answer

Flow in a turbulent boundary layer

Answer

Flow in a stirred tank with high agitation

Question 44

In lubrication analysis, the Hertzian contact theory is used to:

Accepted Answer

Calculate the contact area between two elastic curved surfaces

Answer

Determine the load-carrying capacity of a bearing

Answer

Predict the friction coefficient between two sliding surfaces

Answer

Estimate the lubricant's viscosity

Question 45

The Navier-Stokes equations describe:

Accepted Answer

The motion of viscous and incompressible fluids

Answer

The flow of inviscid and compressible fluids

Answer

The transfer of momentum and energy

Answer

The behavior of elastic and plastic solids

Question 46

In a Couette flow, the velocity profile is:

Accepted Answer

Linear

Answer

Parabolic

Answer

Exponential

Answer

Hyperbolic

Question 47

In a fully developed laminar pipe flow, the velocity profile is:

Accepted Answer

Parabolic

Answer

Linear

Question 48

In boundary layer flow, the region where viscous effects are minimal is known as the:

Accepted Answer

Inviscid region

Answer

Viscous region

Answer

Wake region

Answer

Separated region

Question 49

The dimensionless group that characterizes the relative significance of convective to diffusive heat transfer is known as the:

Accepted Answer

Peclet number

Answer

Nusselt number

Answer

Prandtl number

Answer

Grashof number

Question 50

In a thrust bearing, the load is primarily supported by:

Accepted Answer

Pressure generated by the rotating surface

Answer

Gravity

Answer

Shear forces

Answer

Normal forces

Question 51

In boundary layer theory, which parameter indicates the relative importance of inertia and viscous forces?

Accepted Answer

Reynolds number

Answer

Boundary layer thickness

Answer

Shear stress

Answer

Friction factor

Question 52

Which of the following statements correctly describes the behavior of non-Newtonian fluids?

Accepted Answer

Their viscosity varies with changes in shear stress or shear rate.

Answer

Their viscosity remains constant under varying shear rates.

Answer

They exhibit no viscous behavior.

Question 53

In designing a microfluidic device, how do the choice of material and the design of channel geometry affect the viscous behavior of the fluid being manipulated?

Accepted Answer

Both material choice and channel geometry can influence the fluid's viscosity and flow rate.

Answer

Material choice and channel geometry have no impact on the fluid's viscous properties.

Answer

Material choice primarily influences the fluid's viscosity, while channel geometry primarily affects the flow rate.

Answer

Channel geometry primarily determines the fluid's viscosity, while material choice primarily influences the flow rate.

Question 54

In a laminar boundary layer, the velocity profile is:

Accepted Answer

Parabolic

Answer

Linear

Answer

Sinusoidal

Answer

Exponential

Question 55

What does the Reynolds number represent?

Accepted Answer

Ratio of inertial to viscous forces

Answer

Ratio of inertial to gravitational forces

Answer

Ratio of pressure to viscous forces

Answer

Ratio of viscous to gravitational forces

Question 56

A common application of lubrication is to:

Accepted Answer

Reduce friction in bearings

Answer

Improve heat transfer

Answer

Generate lift

Answer

Increase fluid flow

Question 57

Which factor differentiates laminar from turbulent flows?

Accepted Answer

Velocity profile and energy dissipation

Answer

Flow direction

Answer

Fluid density

Answer

Fluid viscosity

Question 58

When is the Stokes drag law applicable?

Accepted Answer

Low Reynolds number flows around spherical objects

Answer

Flows with strong pressure gradients

Answer

Flows in porous media

Answer

High Reynolds number flows around streamlined objects

Question 59

What does the no-slip condition imply?

Accepted Answer

Fluid velocity at solid boundaries is zero

Answer

Fluid pressure at solid boundaries is zero

Answer

Fluid density at solid boundaries is zero

Answer

Fluid temperature at solid boundaries is zero

Question 60

Which assumption is crucial for the boundary layer approximation?

Accepted Answer

Flow is predominantly parallel to the solid boundary

Answer

Fluid is incompressible

Answer

Flow is steady

Answer

Viscosity is constant

Question 61

In laminar flow, the velocity gradient is:

Accepted Answer

Linear

Answer

Quadratic

Answer

Hyperbolic

Answer

Exponential

Question 62

Which of the following is NOT a dimensionless parameter used in viscous flow analysis?

Accepted Answer

Stress tensor

Answer

Prandtl number

Answer

Reynolds number

Question 63

In boundary layer theory, the region where viscous effects are significant is known as the:

Accepted Answer

Boundary layer

Answer

Shear layer

Answer

Wake region

Answer

Attached flow region

Question 64

The Navier-Stokes equations are a set of partial differential equations that describe the:

Accepted Answer

Motion of viscous fluids

Answer

Flow of inviscid fluids

Answer

Elasticity of materials

Answer

Heat transfer in solids