1. Which of these is a result of Kelvin’s Theorem is essentially?
a) Frozen Vortex Lines
b) Vorticity
c) Circulation
d) Lift
Explanation: Kelvin’s theorem can be used to prove Helmholtz theorems, one of which says ‘vortex lines move with the fluid’ which is what is known as “frozen vortex lines”.
2. In reality, the starting vortex dies out. Why?
a) Lift becomes zero
b) At later times, Kelvin’s theorem is not applicable
c) Due to Viscosity
d) This assumption is wrong. Starting vortex never dies
Explanation: Starting vortex cannot form in inviscid medium. It can form only in a viscous medium. In a viscous medium, it dies instantly due to viscous effects.
3. Generation of lift over an airfoil and formation of starting vortex is correctly explained by which of these?
a) Kutta-Joukowski Theorem
b) Kutta Condition and Kelvin’s Theorem
c) Kutta-Joukowski Theorem and Kelvin’s Theorem
d) Kutta Condition and Helmholtz Theorem
Explanation: Kutta condition enforces smooth flow at the trailing edge. In doing so high velocity gradients formed at the trailing edge generates vorticity and hence circulation is there. From Kelvin’s circulation theorem starting vortex is formed to conserve circulation.
4. Is symmetric airfoil with good lift to drag ratio is used for an aircraft wing?
a) True
b) False
Explanation: The symmetric airfoil with good lift to drag ratio is used for an aircraft wing, this will be translated into lower fuel consumption, shorter take-off and landing times, and shorter runways. Airfoil With backward facing will get high lift coefficient.
5. Is NACA 0012 is symmetric airfoil?
a) True
b) False
Explanation: The NACA 0012 is symmetric airfoil because the mean camber line and chord line intersect in the same line.so, there is no camber in the NACA 0012 airfoil. That the reason the first and second digits are will become zero, and the thickness of NACA 0012 airfoil is 12 percent.
6. What is the thickness of NACA 0002 airfoil?
a) 3%
b) 1%
c) 0%
d) 2%
Explanation: The thickness of the NACA 0002 airfoil is 2 percent. There is no camber in the NACA 0002 airfoil because of the mean camber line and chord line intersect in the same line, so the position maximum camber in the NACA 0002 airfoil is zero.
7. How many types the wake structure is classified?
a) 2
b) 3
c) 5
d) 4
Explanation: The wake structure is classified into five different modes according to their pattern obtained from instantaneous and mean vorticity fields by also taking into account the amplitude spectrum of the lift coefficient.
8. How lift is calculated?
a) Perpendicular to the direction of motion
b) Parallel to the direction of motion
c) opposite to the direction of motion
d) relative to the direction of motion
Explanation: An airfoil shaped body moved through a fluid produces an aerodynamic force. The component of this force perpendicular to the direction of motion is called lift. The lift will oppose the motion and it produces the lift.
9. Is upper and lower curvatures are equal in symmetric airfoil?
a) True
b) False
Explanation: The upper and lower curvature are equal in the symmetric airfoil because there is no maximum camber in the symmetric airfoil when compare to cambered airfoil it does not produce high lift, so these are used in the subsonic flights
10. Is flat bottomed wing is more efficient than fully-symmetrical airfoil?
a) True
b) False
Explanation: The flat bottomed wing is more efficient at low speeds than a fully-symmetrical airfoil with an angle of attack less, so that the reason most of the flat bottomed, under cambered wing uses less power and drag for the same lift.