basic aerodynamics slide share

7/28/2019 Basic Aerodynamics slide share

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The study of objects in motion through air and the

forces that produce such motion.


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INTRODUCTION

Composition of air :-

78% - Nitrogen

21% - Oxygen

1% - Other Gases (argon, carbon

dioxide, hydrogen, helium, neon, etc.)

OXYGEN

Human breathing

Fuel combustion keep aircraft flying


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TROPOSPHERE

Lower level of atmosphereExtends from the surface upward to the tropopause

Contains water vapour that causes

Clouds and vertical air currents

weather

TROPOPAUSE

Boundary between the troposphere and the stratosphere.

Temperature drop with altitude stops and constant

temperature of 56.5

O

C

STRATOSPHERE

Air is extremely thin above troposphere

No water vapour cause no weather.


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DIFFERENT PRESSURE UNIT


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ATMOSPHERIC PRESSURE DECREASES WITH ALTITUDE


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Air is compressible Compressed airmore dense

(less space occupied by air)

Density = measure of air thickness

Density = mass per unit volume

= m/V

The density of gases is governed

by following rules : Density , Pressure

Density , Temperature

Density at sea level is 1.225 kg/m3

DENSITY OF AIR


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AIR TEMPERATURE

o Decrease with increasing altitude

o Constant (-56.5C) above 37 000

ft (11.3 km)

o Decrease at a lapse rate of

1.98C per 1000 ft

o Standard day temperature at sea

level 15C / 59Fo Temperature does not affect

much on aircraft in flight but it

does affect the variations of

humidity

o Humidity affect flight operation.


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HUMIDITY

Amount of water vapour in air (condition of moisture or

dampness)

Temperature influence the maximum amount of water

vapour that the air can hold

Higher air temperature absorb more water vapour

Density of air varies with humidity

Density on damp day (hot day) is less than density on dry

day (cold day)


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TEMPERATURE, PRESSURE, AND DENSITY VERSUS ALTITUDE


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AIR DENSITY AND AIRCRAFT OPERATION

Changes in air density affect the operation of aircraft regardless of

whether the changed density results from changes in pressure,

temperature, humidity, or any combination of these.

If the air density drops there will be a reduction in :

The lift produced by wings.

The thrust produced by propellers or jet engines

The power or torque produced by piston engines.

Significant when

checking engine

operation on

ground


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THE STANDARD ATMOSPHERE

The set of standard conditions is usually known as the

International Standard Atmosphere (ISA).

In the aircraft industry this is also known as the ICAO

Standard Atmosphere.

Table of ISA at sea level


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PRESSURE ALTITUDE

Pressure altitude is the altitude in the standard atmosphere

corresponding to a particular value of air pressure.

The aircraft altimeter is essentially a sensitive barometer

calibrated to indicate altitude in the standard atmosphere.

The symbol Hp is used to indicate pressure altitude.

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