Aerofoil and its Components

If the wing of an airplane is sliced through the leading edge to trailing edge ,the side view would be an airfoil. an airfoil is a device which gets a useful reactions from air moving over its surface. When an airfoil is moved through the air,it is capable of producing lift. Airplane wings,control surfaces,horizontal tail surfaces,vertical tail surfaces,propellers and helicopters rotor blades are all examples of an airfoil. 

The front edge of the airfoil is called the leading edge and tapered rear edge is called the trailing edge. When the mass of air moves through the streamline shape of airfoil,the total air reaction is the source of aerodynamic force. 

 Chord Line: It is the straight line between the maximum curvature of leading edge and trailing edge of the airfoil or the width of the airfoil (wing).

Stagnation Point: When an airplane moves through the mass of air, the particles of air are deflected above and below the aerofoil IE. the wing. The stagnation point is the location on an aerofoil at the leading edge where the airflow divides with some air passing over the top of the aerofoil and rest passing below it. At the stagnation point the velocity of air is almost zero.

As the angle of attack increase the stagnation points moves further down of an aerofoil. This causes greater distance on the top surface from stagnation point to trailing edge. This will result in creation of additional lift. 

Wingspan: The wingspan is the distance from left wing tip to right tip or the length of the wing.

Wing Area: The wing area is a measurement of total surface of the wing. (Wing area=wing span*chord)

Aspect Ratio: The aspect ratio is a ratio of the length of wingspan to its chord (AR=span/chord). The AR has a big role to minimize the induced drag(wing tip vortices).The wing with high aspect ratio generates more lift and less induces drag. Thus,the gliders have wing with high aspect ratio.

Wingtip Vortices: A wingtip vortex is spinning air produced at the tip of the wing ant time the aircraft is producing lift. It is pressure difference on the top and bottom of the wing. Wing tip vortices create the wake turbulence during takeoff and landing of a big jet aircraft. The condensation of moisture as white visible trail on clear sky of a high flying jet is due to wing tip vortices.

Chamber: The wing chamber is defined as the amount of the curvature of an airfoil surface from leading edge to trailing edge. The subsonic airplanes have normally high upper chamber and almost flat lower chamber. The shape of the wing chamber line has very important in determine the aerodynamic characteristics of an airfoil.
When chamber airfoil is moved through the air it provide lift even at 0 degree angle of attack. When the upper and lower chambers of an airfoil are identical,the airfoil is said to be symmetrical. For the symmetrical airfoil and angle of attack has to be positive to produce lift.

Winglet: The winglet is vertical extension on the tips,outboard end of the wing. The winglet increases the efficiency of the wing. It reduces the induced drag by relocating wing tip vortex. The winglet also increases the effective aspect ratio.

Arrow showing Winglet.

Skin Friction: The skin friction is the resistance caused due to the tendency of the air particles to cling on the surface of an airfoil. There are two reasons for this tendency.
1. roughness of the surface of an airfoil
2. due to viscosity of the air.




Boundary Layer: The boundary layer is very thin layer of air adjacent to the wing surface tends to adhere to the wing because of its viscosity.

The viscosity is the resistance to flow,and causes the aerodynamic drag. The air velocity in the boundary layer varies from zero on the surface of the airfoil to the velocity of free stream at the outer edge of the boundary layer.

Various method have been developed to control the boundary. One of then is vortex generator. Vortex generator are small plates standing into the air stream in a row along the airfoil. They tend to delay the breakaway of the boundary layer by re energizing it.