Aerodynamics

Question 1

Define airfoil.

Answer 1

Structural shape that is designed to produce a useful reaction to air movement. 

Question 2

Define cord line.

Answer 2

Imaginary straight line that moves from the leading edge of an airfoil to the trailing edge.

Question 3

Define relative wind.

Answer 3

Wind that is experienced by an airfoil. Created when air moves past the wind foil

Question 4

Define angle of attack.

Answer 4

Angle that occurs between the cord line of an airfoil and the relative wind. Angle of attack is directly related to the production of lift by the airfoil.

Question 5

Define trailing edge. 

Answer 5

The backside of an airfoil.

Question 6

Explain a “stall“.

Answer 6

When the airfoils angle of attack reaches a critical level (20°) it will cause an area of turbulence to expand decreasing lift.

Question 7

What are 4 effects of icing on blades?

Answer 7

The icing specifically:
1) Reduces aerodynamic efficiency of blades
2) Increases loads
3) Vibration - Causes undesirable mechanical vibrations if the icing is uneven
4) Downtime - These conditions could force wind farms to shut down

Question 8

How does “feathering” at low wind speeds protect wildlife?

Answer 8

Blade feathering slows the rotational speed, when the a turbine is below cut in speed, can protect birds and bats without loss of energy.