Aerofoils

Question 1

What three factors affect the pressure distribution of an aerofoil?

Answer 1

The thickness distribution, the centreline camber shape and the AoA.

Question 2

Describe briefly the different ways an aerofoil can stall.

Answer 2

1) Flow can gradually separate at the TE.
2) Flow can separate at the LE abruptly.

Question 3

Describe TE separation in detail.

Answer 3

Flow will separate earlier as the BL is stressed more, e.g. if the AoA increases.
The loss of lift is parabolic.

Question 4

Describe LE separation in detail.

Answer 4

It can occur if the LE is too sharp, or if the aerofoil is very thin.

Question 5

How can transition be delayed for an aerofoil?

Answer 5

RWD loading it, creating a more favourable p gradient.

Question 6

What effects does delaying transition have on an aerofoil?

Answer 6

Decreased Cf and BL thickness, and CoP will move rearwards.

Question 7

What conditions might cause a laminar bubble to occur?

Answer 7

A highly cambered aerofoil, or low camber with high AoA.

Question 8

Describe how laminar bubbles are created.

Answer 8

The laminar BL separates from the aerofoil. The separation causes transition to occur. The turbulent BL reattaches creating an enclosed area of recirculating flow.