Aerodynamics Lab manual

INTRODUCTION

Aerodynamics:

Aerodynamics is the branch of fluid mechanics dealing with air motion and reaction of a body moving within that of air.Aerodynamic centre:

The point in the chord line about which pitching moment is constant. It will not vary with angle of attack.

Airfoil:

The cross section of any surface which can produce aerodynamic lift from the atmosphere.Angle of attack:

Angle between the free stream wind direction and chord line.Angle of incidence:

Angle between the chord line and longitudinal axis of the airplane.Centre of pressure:

The point at which the total resultant pressure force acts.Chord:

It is the straight line joining the leading and trailing edge of an airfoil section.Drag:

It is an aerodynamic force opposing the direction of motion. Drag is inevitable to minimize completely but its effect can be reduced to some extents. It can be due to surface viscosity (friction drag), pressure differences due to shape of an object (form drag), lift acting on a finite wing (induced drag) and other energy loss mechanism in the flow such as wave drag to shockwaves and in efficienciesin engines.

Drag coefficient (CD):

It is defined as drag divided by dynamic pressure multiplied by reference area.

CD = Drag/(Dynamic pressure x Reference area)

Dynamic pressure:

It is product of density and square of velocity divided by two.

Lift:

It is force acting perpendicular to the direction of flight. Force generated by an airfoil section acting at right angles to airstream flowing past it. In level flights lift should be equal to the weight of aircraft.

Lift coefficient:

CL = Lift/Dynamic pressure x Reference Area

NACA Airfoil:

These airfoils are wing cross sections designs invented by NACA organization.Pressure Coefficient:

It is a non dimensional form of pressure.

Stall:

Normally the lift increases with the increase in angle of attack. When angle of attack is reached to a certain value, the flow over the upper surface of the wings separates from the body and the lift starts decreasing even with increase in the angle of attack and this condition (decrease in lift with increase in angle of attack) is called stall.Streamline:

The imaginary line along which the tangent at every point will give velocity at that direction.Wing loading:

Wing loading = The total weight of aircraft/Span area of wing.Wing span:

It is the total length of the wing (measured from wing tip to wing tip)Aspect ratio:

Ratio of span to chord of an airfoil. Hence a high aspect ratio wing has great span and narrow chord and vice versa.

Boundary layer:

The thin layer adjacent to the body where velocity varies from zero on the body and 0.99 V on the edge of the boundary layer.STUDY OF WIND TUNNEL

AIM:

To study about the subsonic wind tunnel (M