Aerodynamics slide
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BASIC AERODYNAMIC Aerodynamic concerns the motion of air and other gaseous fluids and forces acting on objects in motion through the air.
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Transcript of 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
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.
