•    An airfoil is a streamlined body designed in such a way that the separation occurs at extreme rear of the body, producing small wake and consequently small pressure drag.

•    Even for the high Reynolds number, pressure drag is very small whereas the skin friction drag makes major contribution to the total drag.

•    In case of Airfoil, the resulting force is nearly perpendicular to the direction of flow i.e. lift.

•    The lift ad moments on the airfoil are mainly due to the pressure distribution.

An imaginary straight line drawn from the leading edge to the trailing edge of a cross section of an airfoil.

The acute angle between the chord line of the airfoil and the direction of the wind flow. It is denoted by ( )

•    Camber is the curvature of the airfoil from the leading edge to the trailing edge.
•    Upper camber refers to the curvature of upper surface.
•    Lower camber refers to the vurvature of lower surface
•    Mean chamber is the mean line that is equidistance at all points between the upper and lower surface.

The line joining the mid-points of the profile starting from leadig edge and exit at the trailing edge is called as profile centre line.

Aspect ratio:

The ratio of span of the wing to its mean chord is called the aspect ratio of a wing.

A.R.  = Span / Mean chord

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