Boundary Layer Theory Quizzes: Test Your Understanding

Question 1

Which defining feature characterizes a laminar boundary layer?

Accepted Answer

Minimal momentum diffusion

Answer

Elevated shear stresses

Answer

Reversed flow adjacent to the surface

Answer

Intense turbulence

Question 2

Which flow condition is most likely to trigger boundary layer separation?

Accepted Answer

Adverse pressure gradient

Answer

High Reynolds number

Answer

Low Reynolds number

Answer

Smooth surface

Question 3

Define the skin friction coefficient.

Accepted Answer

Ratio of shear stress at the wall to dynamic pressure

Answer

Ratio of velocity at the wall to free-stream velocity

Answer

Ratio of boundary layer thickness to surface roughness

Answer

Ratio of pressure drop to surface area

Question 4

Which factor does NOT influence boundary layer thickness?

Accepted Answer

Fluid compressibility

Answer

Fluid viscosity

Answer

Free-stream velocity

Answer

Surface curvature

Question 5

What is the purpose of the Prandtl mixing length model?

Accepted Answer

Estimating the eddy viscosity in turbulent boundary layers

Answer

Predicting the boundary layer thickness

Answer

Calculating the skin friction coefficient

Answer

Analyzing boundary layer separation

Question 6

According to the definition, the boundary layer thickness, denoted as δ, is the distance from the surface where the velocity is precisely what percentage of the freestream velocity, U∞?

Accepted Answer

99%

Answer

95%

Answer

90%

Answer

80%

Question 7

Which of the following is a dimensionless similarity variable commonly used in boundary layer theory?

Accepted Answer

Eta

Answer

Zeta

Answer

Chi

Answer

Omega

Question 8

Which characteristic describes a laminar boundary layer?

Accepted Answer

Linear velocity profile

Answer

Turbulent fluctuations

Answer

Zero wall shear stress

Answer

Pressure gradient-driven flow

Question 9

Which flow regime exhibits a velocity profile that follows a logarithmic law?

Accepted Answer

Turbulent boundary layer

Answer

Laminar boundary layer

Answer

Transitional boundary layer

Answer

Inviscid flow

Question 10

The Blasius solution describes the:

Accepted Answer

Laminar boundary layer over a flat plate

Answer

Turbulent boundary layer over a cylinder

Answer

Flow in a pipe with a fully developed velocity profile

Answer

Boundary layer separation over a curved surface

Question 11

According to the no-slip condition, where is the fluid velocity zero?

Accepted Answer

At the solid boundary

Answer

At the center of the pipe

Answer

At the free stream

Answer

At the point of separation

Question 12

Under which condition do laminar boundary layers occur?

Accepted Answer

When the Reynolds number is below a critical value

Answer

When the Reynolds number is above a critical value

Answer

When the Reynolds number is equal to a critical value

Answer

When the flow velocity is zero

Question 13

What does the displacement thickness of a boundary layer represent?

Accepted Answer

The vertical distance by which the inviscid flow would be displaced to match the mass flow rate with boundary layer

Answer

The distance within which the velocity profile is 99% of the free stream velocity

Answer

The distance over which the momentum deficit in the boundary layer is equal to the momentum flux outside the boundary layer

Answer

The distance within which the boundary layer equations apply

Question 14

Which of the following factors does NOT influence the boundary layer growth rate?

Accepted Answer

Magnetic field

Answer

Pressure gradient

Answer

Reynolds number

Answer

Surface roughness

Question 15

Which combination of equations is used to derive the boundary layer equations for an incompressible fluid?

Accepted Answer

Navier-Stokes equations and continuity equation

Answer

Bernoulli's equation and continuity equation

Answer

Momentum equation and energy equation

Answer

Laplace's equation and Poisson's equation

Question 16

Which of the following is NOT an application of boundary layer theory in engineering?

Accepted Answer

Nuclear reactions

Answer

Drag reduction in aircraft

Answer

Heat transfer enhancement in heat exchangers

Answer

Flow control in wind turbines

Question 17

Define the boundary layer.

Accepted Answer

A thin fluid layer adjacent to a solid surface where viscous forces dominate

Answer

A region with negligible velocity gradients

Answer

A region with negligible pressure forces

Question 18

Which of the following factors does NOT contribute to boundary layer separation?

Accepted Answer

Smooth surface

Answer

Flow velocity

Answer

Adverse pressure gradient

Answer

Boundary layer thickness

Question 19

What is the main purpose of the boundary layer displacement thickness?

Accepted Answer

To account for the blockage effect of the boundary layer on the external flow

Answer

To predict the onset of boundary layer separation

Answer

To determine the friction drag on the surface

Question 20

Which assumption is essential for the Blasius boundary layer solution?

Accepted Answer

Steady, incompressible, and two-dimensional flow

Answer

No pressure gradient exists

Answer

Viscous dissipation is negligible

Answer

Turbulent flow occurs

Question 21

What is the primary mechanism of momentum transport in turbulent boundary layers?

Accepted Answer

Eddy viscosity

Answer

Shear stress

Answer

Molecular viscosity

Answer

Pressure gradient