Assignment -IIAE612

Jan-April 2015

Q1. Derive the lift and moment coefficients for a thin airfoil whose mean camber line is a circular arc.

Q2. The camber line of a thin airfoil is approximated as two straight lines, where maximum camber is (consider two cases (i)0.04c & (ii) 0.12c). Calculate the lift and moment coefficients for 10o angle of attack. Comment on your results.

Q3. (a) Use the length of two sections in the above problem(Q2) in such a way that the aft part can be considered as flap and find the hinge moment coefficient for the same. (b) Estimate the lift coefficient of a flat plate airfoil at 8o angle of attack having a 30% plain flap deflected at 14o.

Q4. A thin, flat plate airfoil has a 10% leading edge flap and a 25% trailing edge flap. The airfoil is placed at zero angle of attack. Consider following configurations and calculate lift coefficients:

(i) Leading edge flap is only lowered by 8o. (ii) Leading edge flap is lowered by 8o and trailing edge flap is lowered by 10o.(iii) Leading edge flap is lowered by 8o and trailing edge flap is lowered by 15o.(iv) Leading edge flap is lowered by 8o and trailing edge flap is raised by 10o.

Q5. Consider a finite wing with an aspect ratio of 8 and a taper ratio of 0.8. The airfoil section is thin and symmetric. Calculate the lift and induced drag coefficients for the wing when its angle of attack is (i) 5° (ii) 10°. Assume that δ=τ.

Tapered wing

Q6. Consider a rectangular wing with an aspect ratio of 6, and induced drag factor δ =0.055, and a zero lift angle of attack of -2°. At an angle of attack of 3.4°, the induced drag coefficient for this wing is 0.01. Calculate the induced drag for a similar wing at the same angle of attack, but with an aspect ratio of 10. Assume that the induced factors for drag and the lift slope, δ and τ, respectively, are equal to each other. Also, for AR=10, δ =0.105.

Induced drag factor δ as a function of taper ratio. (ct is tip chord and cr is root chord)