Boundary Layer

Question 1

What is a boundary layer?

Answer 1

It is a very thin sheet of air lying over the surface of the wing

Question 2

What is the laminar layer?

Answer 2

The laminar layer is when the boundary layer first flows smoothy over the streamlined shape of the airfoil

Question 3

What is the turbulent layer?

Answer 3

The turbulent layer is when the boundary layer approaches the centre of the wing. This is when the boundary layer starts to lose speed due to skin friction and it becomes thicker and turbulent

Question 4

What is the transition point?

Answer 4

The transition point is when the boundary layer changes from laminar to turbulent

Question 5

What happens to the drag when the boundary layer becomes turbulent?

Answer 5

drag due to skin friction becomes relatively high

Question 6

When does the transition point move forward?

Answer 6

The transition point moves forward when SPEED and the ANGLE OF ATTACK increases

Question 7

List 3 ways to control the boundary layer in order to reduce skin friction

Answer 7

1) suction method
2) laminar airflow
3) Vortex generators

Question 8

What is the suction method?

Answer 8

• series of thin slots in the wing running out from the wing root towards the tip
• Sucks air through the slots preventing the airflow from breaking away from the wing. forces it to follow the curve of the wing’s surface
• air is exhausted backwards to provide extra thrust

Question 9

What is laminar flow airfoil?

Answer 9

it is a structural design intended to make possible better boundary layer control

Question 10

Which part is the thickest part of a laminar flow wing that occurs at the chord?

Answer 10

50% of the chord

Question 11

At which point those the laminar flow of air breaks into a turbulence?

Answer 11

it breaks into a turbulence at or near the thickest part

Question 12

What point is the transition point at which the laminar flow of air becomes turbulent?

Answer 12

the transition point is rearward

Question 13

What are vortex generators?

Answer 13

• They are small plates about an inch deep
• lighter and simpler then the suction boundary bay system
• Tend to prevent or delay breakage of the boundary layer by re-energizing it

Question 14

Where is the vortex generator placed?

Answer 14

standing on edge in a row spanwise along the wing and place at an angle of attack and generate vortices