Incompressible Flow over Airfoils topics include: Airfoil nomenclature and characteristics, vortex sheet, kutta condition, kelvin’s circulation theorem, symmetric and cambered airfoils, modern low speed airfoils, viscous, laminar and turbulent flows. Incompressible flow over airfoils is important for understanding airflow around airfoils. This helps determine the best materials and shapes for wings and propellers for the speed range of the aircraft.  Incompressible flow is a flow where density is constant in both time and space. Although all real fluids are compressible, a flow is often... Show more

Incompressible Flow over Airfoils topics include: Airfoil nomenclature and characteristics, vortex sheet, kutta condition, kelvin’s circulation theorem, symmetric and cambered airfoils, modern low speed airfoils, viscous, laminar and turbulent flows.

Incompressible flow over airfoils is important for understanding airflow around airfoils. This helps determine the best materials and shapes for wings and propellers for the speed range of the aircraft. 

Incompressible flow is a flow where density is constant in both time and space. Although all real fluids are compressible, a flow is often approximated as incompressible if the effect of the density changes cause only small changes to the calculated results. 

Thin airfoil theory is used to analyze incompressible, inviscid flow over airfoils. 
The theory's assumptions are:
Airflow is incompressible
Airflow is inviscid
Airfoil has infinite length
Airfoil has zero thickness 

The theory's equation is: C= 2πα
Where:
CLis the coefficient of lift
α is the angle of attack 

The theory's assumptions eliminate the possibility of drag.

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Aerodynamics Practice Test: Incompressible Flow over Airfoils

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25 Questions

1. Is initial distribution is given by solid curves?

Don't knowTrueFalseMaybe

2. Is fluid flows across the airfoil with a backward facing step?

Don't KnowFalseTrueMaybe

3. A state with flow separation and reducing lift at a high angle of attack is___

LandingClimbingTake offStall

4. The Kutta Condition according to the thin airfoil theory is_____

γ(c)=0γ(ξ )=0γ(x)=0\(\frac {dz}{dx}\)=0

5. Is 17% is the thickness of NASA LS-0417 airfoil?

FalseTrueDon't knowMaybe

6. Is super critical airfoil used to improve the drag at subsonic speed?

TrueFalseMaybeDon't know

7. What parameter is used to decrease the stall speed?

ChordCamberCamber lineChord line

8. The lift per unit span for a thin, cambered airfoil with α=5°, A₀=0.65, A₁=1 is____

L’ = cπ\(V_∞^2\)ρ∞ (-0.35)L’ = cπ\(V_∞^2\)ρ∞ (0.15)L’ = cπ\(V_∞^2\)ρ∞ (1.15)L’ = cπ\(V_∞^2\)ρ∞ (1.65)

9. Is symmetric airfoil with good lift to drag ratio is used for an aircraft wing?

TrueMaybeDon't knowFalse

10. Is flat bottomed wing is more efficient than fully-symmetrical airfoil?

TrueMaybeFalseDon't know

11. Select the incorrect statement for a thin, symmetric airfoil out of the following.

Moment about quarter-chord is zeroMoment about quarter-chord depends on the angle of attackQuarter-chord is the aerodynamic centerQuarter-chord is the center of pressure

12. Is positive camber upper surface is more convex?

TrueMaybeFalseDon't know

13. Which of the following is the correct solution of the transformed fundamental equation of aerodynamics for a symmetrical airfoil?

γ(θ)=2αV∞\(\frac {1-cos⁡\theta }{sin\theta }\) γ(θ)=2αV∞\(\frac {sin⁡\theta }{1+cos\theta }\) γ(θ)=2αV∞\(\frac {cos\theta }{sin\theta }\) γ(θ)=2αV∞\(\frac {1+cos\theta }{sin⁡\theta }\)

14. Identify the missing angle given by the question mark for the following camber distribution of a thin airfoil.

tan-1\(\frac {dz}{dx}\) tan-1–\(\frac {dz}{dx}\)+αtan-1⁡αtan-1⁡-\(\frac {dz}{dx}\)

15. The lift can be calculated accurately using the pressure distribution assuming an inviscid flow.

MaybeTrueDon't KnowFalse

16. The standard NACA airfoils were based on ____

Computer modeling resultsNumerical techniques and wind- tunnel testingExperiment dataTheoretical data

17. What is the purpose of trailing edge?

Vortex are createdAirflow rejoinsAirflow separatedStalling will created

18. For an arbitrary inviscid and incompressible flow, with all the body forces zero, what is best described by the given sketch?

Kelvin’s Circulation TheoremKutta ConditionBoundary Layer FormationGeneration of Lift

19. How the circulation around the airfoil?

PositiveSlightly variesNegativeConstant

20. Is NASA airfoil designed using numerical technique?

FalseTrueMaybeDon't Know

21. The moment coefficient for a thin cambered airfoil about the leading edge is given by______

cm,le=-0.5π(A0+A1-0.5A2)cm,le=-0.5π(2A0+A1)cm,le=-π(2A2+A1)cm,le=-π(A0+A1+A2)

22. The aerodynamic center for all the airfoils lies exactly at the quarter-chord always for all the given angle of attacks.

FalseMaybeTrueDon't know

23. The relation between lift coefficient and moment coefficient about the leading edge is_______

cm,le=-(\(\frac {c_l}{4}\)+(A1-A2))cm,le=-(\(\frac {c_l}{2}+\frac {\pi }{4}\)(A1-A2))cm,le=-(\(\frac {c_l}{4}+\frac {\pi }{4}\)(A1-A2))cm,le=(\(\frac {c_l}{2}+\frac {\pi }{4}\)(A1-A2))

24. The extra term appearing in the thin airfoil theory solution for a cambered airfoil is a______

Fourier sine seriesFull Fourier seriesFourier cosine seriesConstant

25. What is the thickness in NACA 2412 airfoil?

12%2%41%24%