What is a boundary layer?
It is a very thin sheet of air lying over the surface of the wing
What is the laminar layer?
The laminar layer is when the boundary layer first flows smoothy over the streamlined shape of the airfoil
What is the turbulent layer?
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
What is the transition point?
The transition point is when the boundary layer changes from laminar to turbulent
What happens to the drag when the boundary layer becomes turbulent?
drag due to skin friction becomes relatively high
When does the transition point move forward?
The transition point moves forward when SPEED and the ANGLE OF ATTACK increases
List 3 ways to control the boundary layer in order to reduce skin friction
1) suction method
2) laminar airflow
3) Vortex generators
What is the suction method?
- 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
What is laminar flow airfoil?
it is a structural design intended to make possible better boundary layer control
Which part is the thickest part of a laminar flow wing that occurs at the chord?
50% of the chord
At which point those the laminar flow of air breaks into a turbulence?
it breaks into a turbulence at or near the thickest part
What point is the transition point at which the laminar flow of air becomes turbulent?
the transition point is rearward
What are vortex generators?
- 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
Where is the vortex generator placed?
standing on edge in a row spanwise along the wing and place at an angle of attack and generate vortices
