Aerodynamics Mcqs - Set 10

ANSWER: Large number of unsteady 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.

ANSWER: to find a numerical method

Explanation:
The purpose of non-lifting flow over an arbitrary bodies is to find a numerical method for appropriate solution on a high speed digital computer. The technique is called the source panel. The numerical solution of potential flows by both source and vortex panel techniques has revolutionized the analyses of low speed flows.

ANSWER: False

Explanation:
The shape of an arbitrary body depends on the distribution of singularities which in combination with a uniform stream, produce the flow over the given body.T he purpose of this elementary flow is to present such a direct method, limited for the present to non-lifting flows.

ANSWER: True

Explanation:
The numerical method for an appropriate solution on high speed digital computer. This technique is called source panel method, which, since the late 1960’s, has become a standard aerodynamic tool in industry and most research laboratories.

ANSWER: True

Explanation:
The numerical solution of potential flows by both source and vortex panel techniques has revolutionized the analysis of low-speed flows. The purpose of the numerical solution is to introduce the basic ideas of the source panel method, which is a technique for the numerical solution of non-lifting flows over arbitrary body.

ANSWER: True

Explanation:
The strength of an infinitesimal portion of the sheet. This is small section of the source sheet can be treated as a distinct source of strength. The flow is located at a distance from dx. The carterian coordinates of ‘P’ are (x, y). This is the small section of the source sheet of strength xds induces an infinitesimally small potential.

ANSWER: True

Explanation:
By integrating from a to b the complete velocity potential is obtained at point p and it can change from position to negative along the sheet, that is the source sheet is really a combination of line source and line sinks.

ANSWER: True

Explanation:
Source sheet is used to cover the surface of the arbitrary body were the strength varies in such a fashion that the combined action of the uniform flow and the source sheet makes the airfoil surface as stream line of the flow.

ANSWER: It allows it to varies from one panel to next panel

Explanation:
The source strength ‘X’ per unit length be constant over a given panel but allow it to vary from one panel to the next, that if there are total n panel. The source panel strength per unit length is ‘Xn’. Therefore boundary condition is imposed numerically by defining the midpoint of each panel.

ANSWER: True

Explanation:
The boundary condition is applied at the control point that is the normal component of the flow velocity is zero at the control points. This component of freestream velocity is perpendicular to the panel and ‘n’ be the unit volume to the ith panel directed out of the body.

ANSWER: True

Explanation:
The direction of the outward unit normal vector is positive when directed away from the body and it is carried out in the denominator at a singular point arises on the ith panel because the control point itself can be the contribution to the j=1 panel.

ANSWER: Sum of the freestream

Explanation:
The normal component of the flow velocity at the rth control point is the sum of that due to the free stream and that due to the source panels. The boundary condition stats that this sum must be zero and it is the cruse of the source panel method.

ANSWER: NACA 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.

ANSWER: to increase maximum lift

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.

ANSWER: True

Explanation:
The shape of the airfoil depends on the thickness of the airfoil. The thickness of an airfoil varies along the chord. The thickness is measured perpendicular to the chord line. In NACA series the last two digits indicate the percentage of thickness.

ANSWER: Distance between leading edge and trailing edge

Explanation:
Distance between leading edge and the trailing edge is called chord. Chord refers to the imaginary straight line joining the leading edge and trailing edge of an airfoil. The chord length is the distance between the trailing edge and the point on the leading edge, where the chord intersects the leading edge.

ANSWER: allow the wing to operate at high angle of attack

Explanation:
Leading edge is a part of the airfoil. Leading edge allows the wing to operate at a high angle of attack. Slats are placed at the leading edge. These are aerodynamic surfaces on the leading edge of the wing. These are high lift devices used for short takeoff.

ANSWER: Airflow rejoins

Explanation:
Trailing edge is a part of airfoil. Trailing edge of an aerodynamic surface such as awing is its rear edge. Where the airflow will separate at the leading edge and rejoins at the trailing edge. Ailerons are placed at the trailing edge of the wing and rudder, elevator is placed at the trailing edge of tail.

ANSWER: Circular

Explanation:
The shape of the airfoil at the leading edge is usually circular with a leading edge radius of approximately 0.02c. The shape of all standard NACA airfoils are generated by specifying the shape of the mean chamber line and then wrapping specified symmetric thickness distribution around the mean camber line.

ANSWER: 12%

Explanation:
The NACA 2412 airfoil has a maximum camber of 2% located at 40% from the leading edge with a maximum thickness of 12%. It was the first 4-digit NACA series and it was developed in 1930’s because of the 12% thickness the shape of the airfoil is symmetric.