1. Define Kutta-Joukowski theorem.
a) Lift per unit span on the airfoil
b) Drag per unit span on the airfoil
c) Moment per unit span on the airfoil
d) Thrust per unit span on the airfoil
Explanation: The Kutta-Joukowski theorem states that lift per unit span on a Two-Dimensional body, is directly propositional to the circulation around the body. It is a fundamental theorem of aerodynamics used for the calculation of the lift of an airfoil and any two-dimensional body.
2. What is the angle of attack of lift producing airfoil?
a) Angle of attack less than zero
b) Angle of attack greater than zero
c) Angle of attack is zero
d) Angle of attack remains the same
Explanation: A lift producing airfoil either has camber or is translating in a uniform fluid at an angle of attack greater than zero. Moreover, it must have a sharp trailing edge. An airfoil generates lift by exerting a downward force on the air as it flows past.
3. How the fluid moves on the airfoil?
a) Lower surface
b) Upper and middle surface
c) Upper surface
d) Lower and upper surface
Explanation: Fluid moving along the lower and upper surface of the airfoil should meet at the sharp trailing edge. Since viscous dissipation prevents the fluid to turn around the sharp edge. This is known as the Kutta-Condition for real flow.
4. What is the condition for Kutta and Joukowski theorem?
a) Pressure and lift
b) Pressure and drag
c) Drag and lift
d) Lift and moment
Explanation: Kutta and Joukowski discovered that for computing, the pressure and lift of a thin enough airfoil for flow with large enough Reynolds number and at small enough angle of attach the flow can be assumed inviscid in the entire region provided the Kutta condition is imposed.
5. What is the flow outside the airfoil?
a) Irrotational
b) Rotational
c) Circumferential
d) Constant
Explanation: The flow outside the airfoil is irrotational and the circulation around any closed curve not enclosing airfoil is consequently zero. When the boundary layer separates, its displacement thickness increases sharply, which modifies the outside potential flow and pressure field.
6. How rotating flow is induced?
a) Joint effect of airfoil
b) Joint effect of chord
c) Joint effect of camber
d) Joint effect of camber line
Explanation: Rotating flow is induced by the joint effect of camber, angle of attack and sharp trailing edge of the airfoil and should not be confused with a vortex like a tornado encircling the cylinder or wing of an airplane in flight.
7. Kutta-Joukowski theorem refers to __________
a) two-dimensional flow around an airfoil
b) one-dimensional flow around an airfoil
c) three-dimensional flow around an airfoil
d) flows around an airfoil
Explanation: Kutta-Joukowski theorem refers to Two-Dimensional flow around an airfoil and determines the lift generated by one unit of a span. Kutta-Joukowski theorem is an inviscid theory, but it is a good approximation for real viscous flow in typical aerodynamic applications.
8.What is the condition for rotational flow in Kutta-Joukowski theorem?
a) Small number of unsteady flow
b) Large number of unsteady flow
c) Large number of steady flow
d) Small number of steady flow
Explanation: When there are free vortices outside of the body as may be the case for a large number of unsteady flow, the flow is rotational. A fluid is said to be rotational if fluid particles are rotating about their own mass center, otherwise, flow is irrotational.
9. Who designed the nomenclature of airfoil?
a) NACA series
b) EULAR series
c) EPPLER series
d) CLARK series
Explanation: The nomenclature of airfoil is designed by the NACA series. The shape of the NACA airfoil is described using a series of digits following the word NACA. The NACA identified different airfoils shape with a logical numbering system, such as symmetric airfoil and cambered airfoil.
10.Purpose of camber in an airfoil is ____________
a) to increase maximum drag
b) to increase maximum lift
c) to decrease maximum lift
d) to decrease maximum drag
Explanation: The main purpose of camber is to increase the maximum lift in an airfoil. The maximum lift coefficient can get by increasing the camber in an airfoil. Some recent design use negative camber. That airfoil is called the supercritical airfoil. This type of airfoil is used in the supersonic flight and to produce a higher lift to drag ratio.