Ch 5 - Aerofoil Pressure Distribution

Question 1

Magnitude and Reaction of the Total Reaction is influenced by:

Answer 1

• Pressure Distribution of the Aerofoil
  Influenced by: - Speed of airflow
  - Angle of Attack
  - Camber of the Aerofoil
• Area of Aerofoil

Question 2

Effect of increasing the AoA on a Cambered Aerofoil

Answer 2

Increasing angle of attack leads to:

• C of P moves forward
• Stagnation points moves round and down (underside)
• Peak Suction Point Moves forward
• Drag increases (form drag)
• Increased Total Reaction

Question 3

Effect of increasing AoA on Symmetrical Aerofoil:

Answer 3

• Increased Total Reaction
• CoP does not move
• Magnitude of P change varies with speed of airflow

Increased Speed = Increased pressure change

Question 4

Increasing the Camber…

Answer 4

Increases the pressure differential

• Pattern of the pressure differential determines the position of the CofP
• > AoA and camber, not flow speed

Question 5

Stagnation Point

Answer 5

Is the point at which the Dynamic Pressure = 0 on the surface of the Aerofoil

• Airflow perpendicular to the surface and brought to 0m/s

Static Pressure Increases

Question 6

Aerodynamic Force Coefficient

Answer 6

Cf - Dimensionless number used to balance the equarion

Aerodynamic Force = Pressure x Area (S)

A product of pressure distribution

Question 7

Aerodynamic Force Equation

Answer 7

F=qSCf
q=Dynamic Pressure
S= Surface area of the Aerofoil
Cf= Coefficient of aerodynamic force

Cf= F/ qS. Or Cf = p/q (where p= Aerodynamic Surface Pressure)

Question 8

Component of Aerodynamic Force

Answer 8

A dimensionless ratio of surface pressure to outside pressure

Cf = p/q = Surface Pressure / Dynamic Pressure

Cf has 2 components: Cl (coefficient of Lift)
Cd (Coefficient of drag)
Cdi (coe. Induced drag)
Cdp (coe. Skin friction / Form drag)