Engineering Questions with Answers - Multiple Choice Questions
Aerodynamics – Airfoil Characteristics
1 - Question
Does lift and drag of an airfoil depend on angle of attack?
Explanation: The lift and drag of an airfoil depend not only on the angle of attack but also on the shape of the airfoil. The lift coefficient and drag coefficient depend on the shape of the airfoil and will alter with changes in the angle of attack and other wing appurtenance.
2 - Question
How lift and drag ratio can be expressed in a relation?
a) Dividing the lift coefficient by the drag coefficient
b) Dividing the lift coefficient by the moment coefficient
c) Dividing the drag coefficient by the lift coefficient
d) Dividing the drag coefficient by the moment coefficient
Explanation: The lift-drag ratio is used to express the relation between lift and drag, and is obtained by dividing the lift coefficient by the drag coefficient. We can get the maximum lift coefficient by the drag coefficient for a given airfoil. The characteristics of any airfoil section can conveniently be represented by a graph showing the lift-drag ratio.
3 - Question
What is the graph that is represented in the airfoil section?
a) Lift-moment ratio
b) Coefficient of lift-coefficient of drag ratio
c) Angle of attack-drag ratio
d) Lift–angle of attack ratio
Explanation: The characteristics of any particular airfoil section can conveniently be represented by a graph, showing the amount of lift and drag obtained at a various angle of attack, the lift-drag ratio, and the movement of the center of pressure. With these graphs, we can choose suitable airfoil for the aircraft.
4 - Question
Define stalling angle in the graph.
a) The curve increases maximum at a particular section and decreases rapidly in the same section
b) The curve increases at different section and decreases rapidly at different section
c) The curve remains constant at all section
d) Lift curve will increases and drag curve will remain constant
Explanation: The lift curve reaches its maximum for any wing section at certain degree of angle of attack and then rapidly decreases at some degree of angle of attack is therefore the stalling angle. Stalling will occurs at particular degree were the maximum lift will be achieved by the aircraft at that point stalling will takes place.
5 - Question
Define drag curve.
a) Drag will increase rapidly at particular degree of angle of attack and overcomes the lift curve at particular degree of angle of attack
b) Drag curve will decrease at particular degree of angle of attack and lift curve increasing at particular degree of angle of attack
c) Drag curve remains constant and lift curve will be increasing
d) Lift curve remains constant and drag curve will be increasing
Explanation: The drag curve increases very rapidly at a certain degree of angle of attack and completely overcomes the lift curve at some degree of angle of attack, at this point maximum drag will be caused.so, at this point lift will drastically decrease and hence producing the drag over the body.
6 - Question
Is lift to drag ratio, maximum at zero degrees angle of attack?
Explanation: The lift-drag ratio will reach its maximum at zero degree angle of attack, at this angle we obtain the most lift for less amount of drag.so, that the aircraft will get maximum amount of lift at zero angle of attack.
7 - Question
Is airfoil shape similar to blades of the propeller?
Explanation: An airfoil is the shape of a wing, blade of a propeller, rotor, and blades of a turbine. A propeller is a type of fan that transmit power by converting rotational motion in its thrust.A pressure difference is produced between the forward and rear surface of the airfoil-shape and fluid is accelerated behind the blade.
8 - Question
How propeller creates a thrust force?
a) With transmitted power
b) With own power
c) With the existing power
d) With supplied power
Explanation: A propeller creates a thrust force out of the supplied power. The magnitude of this force is not for a given propeller but depends on the velocity of the incoming air and the rotational velocity of the propeller and helps the propeller to create the forward thrust.
9 - Question
Is airfoil can be characterized by the relation between the angle of attack, lift coefficient and drag coefficient?
Explanation: Airfoil can be characterized by the relation between an angle of attack, lift coefficient and drag coefficient. Where a propeller can be described in terms of advance ratio, thrust coefficient and power coefficient. The efficiency which corresponds to the lift-drag ratio of a wing can be calculated from these coefficients.
10 - Question
Is axial compressor is a compressor that can continuously pressurize gasses?
Explanation: An axial compressor is a compressor that can continuously pressurize gases. It is a rotating airfoil based compressor which the gas principally flows parallel to the axis of rotation .this diffuse from other rotating compressor. Such as centrifugal compressor, axial centrifugal compressor and mixed flow compressors .where the fluid flow will include a radial component through the compressor.
11 - Question
Turbine blades are used to extract energy from the high temperatures.
Explanation: The turbine blades are responsible for extracting energy from the high temperature, high pressure gas produced by the compressor to survive in this difficult environment, turbine blades often use exotic material like super alloy and many different methods of cooling. Such as boundary layer cooling and thermal barrier coatings.