7/30/2019 Aerodynamic Propulsion and Flight Machines - 2003

1/10

7/30/2019 Aerodynamic Propulsion and Flight Machines - 2003

2/10

Aerodynamics is a branch of dynamics concerned

with studying the motion of air, particularly when it

interacts with a solid object.

Aerodynamics is a subfield of fluid dynamics andgas dynamics, with much theory shared between

them.

Aerodynamics is often used synonymously with gas

dynamics, with the difference being that gas

dynamics applies to all gases.

7/30/2019 Aerodynamic Propulsion and Flight Machines - 2003

3/10

Aerodynamic problems can be classified according to

the flow environment. External aerodynamics is thestudy of flow around solid objects of various shapes.

Evaluating the lift and drag on an airplane or theshock waves that form in front of the nose of a rocketare examples of external aerodynamics. Internalaerodynamics is the study of flow through passages in

solid objects. For instance, internal aerodynamics encompasses the

study of the airflow through a jet engine or throughan air conditioning pipe.

7/30/2019 Aerodynamic Propulsion and Flight Machines - 2003

4/10

Aerodynamic problems can also be classified accordingto whether the flow speed is below, near or above the

speed of sound. A problem is called subsonic if all the

speeds in the problem are less than the speed of sound,

transonic if speeds both below and above the speed ofsound are present (normally when the characteristic

speed is approximately the speed of sound), supersonic

when the characteristic flow speed is greater than the

speed of sound, and hypersonic when the flow speed ismuch greater than the speed of sound. Aerodynamicists

disagree over the precise definition of hypersonic flow;

minimum Mach numbers for hypersonic flow range

from 3 to 12.

7/30/2019 Aerodynamic Propulsion and Flight Machines - 2003

5/10

The influence of viscosity in the flow dictates a

third classification.

Some problems may encounter only very smallviscous effects on the solution, in which case

viscosity can be considered to be negligible.

The approximations to these problems arecalled inviscid flows. Flows for which viscosity

cannot be neglected are called viscous flows.

7/30/2019 Aerodynamic Propulsion and Flight Machines - 2003

6/10

An aircraft is a vehicle that is able to fly by gainingsupport from the air, or, in general, the atmosphere

of a planet. It counters the force of gravity by using

either static lift or by using the dynamic lift of an

airfoil, or in a few cases the downward thrust from

jet engines.

Although rockets and missiles also travel through

the atmosphere, most are not considered aircraftbecause they do not have wings and rely on rocket

thrust as the primary means of lift.

7/30/2019 Aerodynamic Propulsion and Flight Machines - 2003

7/10

The human activity that surrounds aircraft is

called aviation. Manned aircraft are flown by

an onboard pilot. Unmanned aerial vehicles may be remotely

controlled or self-controlled by onboardcomputers.

Aircraft may be classified by different criteria,such as lift type, propulsion, usage, andothers.

7/30/2019 Aerodynamic Propulsion and Flight Machines - 2003

8/10

A helicopter (informally known as a "chopper") is atype of rotorcraft in which lift and thrust are

supplied by one or more engine-driven rotors. This

allows the helicopter to take off and land vertically,

to hover, and to fly forwards, backwards, and

laterally.

7/30/2019 Aerodynamic Propulsion and Flight Machines - 2003

9/10

These attributes allow helicopters to be used

in congested or isolated areas where fixed-

wing aircraft would usually not be able totake off or land.

The capability to efficiently hover forextended periods of time allows a helicopter

to accomplish tasks that fixed-wing aircraftand other forms of vertical takeoff andlanding aircraft cannot perform.

7/30/2019 Aerodynamic Propulsion and Flight Machines - 2003

10/10