Aerodynamics slide

BASIC AERODYNAMICAerodynamic concerns the motion of air and

other gaseous fluids and forces acting on objects

in motion through the air.

BASIC AERODYNAMIC

The science of the action of air on an

aircraft.

Newton’s Laws of Motion

Every objects persist in its state of rest or uniform motion in a straight line unless it is compelled to

change that state by force impressed on it.

Newton’s Laws of Motion

A body will accelerate with

acceleration proportional to the force and inversely proportional

to the mass.

constant massForce = mass x acceleration

Force = mass x change in velocity with time

The motion of an aircraft resulting from aerodynamic forces and the aircraft weight and thrust can be

computed by using Newton’s 2nd Laws of motion.

Differential formForce = change of momentum with change of time

Newton’s Laws of Motion

For every action, there is an equal and opposite re-action.

Bernoulli's principle

Increase in the velocity of flow will result in a decrease

in the static pressure.

Bernoulli's principle

AIRFOIL

THE SHAPE OF THE MEAN CAMBER

AIRFOIL TERMINOLOGY• THE MEAN CAMBER LINE• THE CHORD LINE• THE CHORD• THE MAXIMUM THICKNESS• AERODYNAMIC FORCE• CENTER OF GRAVITY• THE AERODYNAMIC CENTER• THE CENTER OF PRESSURE• FLIGHT PATH • RELATIVE WIND• ANGLE OF ATTACK

THE MEAN CAMBER LINE

is a line drawn midway between the upper and lower surfaces

THE CHORD LINE

THE CHORD

The length of the chord line and is the characteristic dimension of

the airfoil section.

THICKNESS

AERODYNAMIC FORCE

AERODYNAMIC CENTER

Moment about the aerodynamic center is constant with angle.

Aerodynamic center does not move with angle.

CENTER OF PRESSURE

Aerodynamic force acts through the center of pressure.Center of pressure moves with angle of attack.

CENTER OF GRAVITY

The total weight of the airplane and its loads is distributed throughout the

aircraft and concentrated at one given point

FLIGHT PATH

RELATIVE WIND

• Relative wind is the "wind" that acts exactly opposite to the direction of flight.

• In the picture to the left the relative wind is horizontal so this airplane is in level flight.

RELATIVE WIND

• Notice that when the airplane climbs the drag vector is still parallel to the relative wind - as shown. In this case the drag is no longer horizontal.

RELATIVE WIND

• The airplane is descending. Once again you can see that the drag vector acts parallel to the relative wind.

ANGLE OF ATTACK The angle between the chord line relative to wind direction.

ANGLE OF ATTACK

DEVELOPMENT OF AERODYNAMIC FORCES

THE USE OF THE POWER AND FLIGHT CONTROLS

FOR CHANGING THE FORCES OF LIFT,

WEIGHT, THRUST AND DRAG.

AILERON

Rolling Motion

Rolling

Elevator – Horizontal Stabilizer

Pitching Motion

Pitching

Rudder - Vertical Stabilizer

Yawing Motion

Yawing

FORCES ACTING ON AIRCRAFT IN FLIGHT

•LIFT•WEIGHT•THRUST •DRAG•CENTRIFUGAL FORCE

WHAT IS LIFT ?

WHAT IS WEIGHT ?

WHAT IS THRUST ?

WHAT IS DRAG ?

PRESSURE PATTERNS

PRESSURE PATTERNS

PRESSURE PATTERNS

PRESSURE PATTERNS

INDUCE DRAG

Upwash and downwash fields

around an airplane create turbulence in

flight

WINGLETWinglets can be used to

produce extra lift, besides lower drag. Mounted on the

rear part of the wing to minimize interference

effects.Drag reduction rates are of the order of 5 %.

Since there are two different ways that lift is produced, there are also

two different types of induced drag :

dynamic drag (Newtonian) and pressure drag

(Bernoulli).

DYNAMIC DRAG

PRESSURE DRAG

There are also skin-friction drag and form drag, which are referred to as parasite drag.

All drag other than induced drag is parasite drag.   

PARASITE DRAG

SPEED BRAKE

LIFT DUMPER

PROFILE DRAG

The dihedral angle is the angle made between one wing and the horizontal, as

viewed from the nose or tail of the aircraft.

DIHEDRAL ANGLE

Dihedral is applied for purposes of stability.

UNHEDRAL ANGLE

Where the wings are set an angle such that the tips are lower than the

centre. The opposite of DIHEDRAL.

C-17 GlobemasterLarge transport aircraft with four jet

engines. Able to take off or land in short distances.

POLYHEDRAL ANGLE

A form of dihedral in which there are one or more

changes of dihedral in each wing panel.

FIX WING AERODYNAMICS

CONSTRUCTION

Cantilever Wing

Cantilever Wing

HIGH LIFT DEVICES

F L A P S

Slat and Slot

Flaps and Slat

Slotted Wing

DEFINITION

The amount of drag depends on :

1. Size of the aircraft. 2. Details of the shape and smoothness

of the aircraft.3. Lifting efficiency of the wing. 4. Dynamic pressure ( density and

speed ).

TYPES OF DRAG

There are three main types of drag affecting performance of an aircraft:

• Induced drag.•Skin friction of parasitic drag.•Wave drag.

Induce Drag

• Induced drag is the most important form of drag because it occurs as a result of the force of lift which enables a plane to remain airborne.

• The backward force on the plane is the induced drag force.

Skin Drag• Skin friction or parasitic drag is a

simple kind of drag that results from wind resistance to the rough surfaces of an aircraft. For example, when an F-16 is loaded up with weapons and fuel tanks, the plane’s aerodynamics are complicated.

• This creates drag which will affect flight performance and G forces – that is, forces of acceleration that pull a pilot when he or she is in motion.

Wave Drag• Wave drag is only found in jet

fighters or supersonic aircraft. When a plane moves at supersonic speeds, it builds up a tremendous front. A huge amount of energy is required to move through these waves and this resistance is called wave drag.

• When the resulting shock wave hits the ground, it is experienced by people of the ground in the rattling form of a “sonic boom.”

FORCES AFFECTING PERFORMANCE

VARIATION FACTORS

•Change in weight•Configuration•Altitude

CONFIGURATIONvs

PERFORMANCES• Accomplished by lowering the landing

gear, adding external stores, extending speed brakes multiplied the area by the dynamic pressure of the airstream is the parasite drag.

• Increase drag requires more power to maintain a certain velocity n affects the range and endurance because higher fuel consumption.

ALTITUDEvs

PERFORMANCES

• Increase in altitute – Decrease in air density.

• Increase in velocity without increasing the drag force.

•Higher true airspeed.

WINDS vs PERFORMANCES

Winds must be considered because of

their effect on the ground speed.

Relative Velocity

Relative Velocity

SPEED REGIMES

SPEED OF SOUND

Shock Waves

The air pressure waves move away from the airplane in all

directions at the speed of sound pile up ahead of the airplane and compress and

then move out and back from the plane, towards the

ground.

Sound Barrier•The sudden increase in air

resistance, aerodynamic drag that occurs when an aircraft approaches the speed of sound. This is also called the sonic barrier.

•The speed of sound is 758 miles / hour (1220 km / hour.