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MEL 715 : GAS DYNAMICS

P M V Subbarao

Associate Professor

Mechanical Engineering Department

I I T Delhi

A Passion of Doing Adventures lead to a

Hi-Fi Science and Technology!!!

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The Shocking News

People had dreamed of flying for many years.

A Shocking News ?#$?%? 1 million to 10 million years they might be able to make a

plane that would fly ?!?!?!

The United States Army was trying to develop an airplanein 1903, but the plane wouldn't fly.

The New York Times wrote that maybe in1 million to 10 million years they might be able to make a

plane that would fly.

Only eight days later two men were successful in flying thefirst manned plane.

They were Wilbur Wright and his younger brother, Orville.

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A Narrow Gap Between Possibility & Impossibility

The would-be aeronauts of the nineteenth century closely

studied the flight of birds and began building flying machines

patterned after avian structures.

Their birdlike craft failed miserably.

They quickly realized that in reality they knew nothing about the

lift and drag forces acting on surfaces cutting through the

atmosphere.

To fly, man first had to understand the flow of air over aircraft

surfaces.

This meant that he had to build instrumented laboratories in

which wings, fuselages, and control surfaces could be testedunder controlled conditions.

Thus it is not surprising that the first wind tunnel was built a full

30 years before the Wrights' success at Kitty Hawk.

A science called Aerodynamics leading to Gas dynamics.

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Motivating Examples

Re-entry flows

Rocket Nozzle Flows

Jet Engine Inlets

Celestial Gas Flows Volcanic Gas flows..

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Descent of A Spacecraft

http://mars.jpl.nasa.gov/msl/mission/images/Entry1.jpg

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Landing of A Space Craft

http://mars.jpl.nasa.gov/msl/mission/images/Entry2.jpg

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Applicability of Continuum Theory

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Entry Interface Gas Dynamics

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Re-Entry

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Gas Dynamics of Re-entry

A range of phenomena are present in the re-entry of

a vehicle into the atmosphere.

This is an example of an externalflow.

Bow shock wave : Suddenlyraises density,

temperature and pressure of shocked air; consider

normal shock in ideal air

ro= 1:16 kg/m3 to rs= 6:64 kg/m3 (over five times asdense!!)

To = 300 K to Ts= 6100 K(hot as the sun's surface

!!)

Po = 1:0 atm !to Ps= 116:5 atm (tremendous force

change!!)

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Rockets : An Example of Internal Flow

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Rocket Nozzle Flows

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Jet Engines

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Supersonic Jet Engines

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Supersonic Jet Engine Inlets

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Volcanic Gas Dynamics

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Propagation of a Pulsed Protostellar Jet

Protostellar jets are unique in that they have high Mach numbers, are

overdense compared to their surroundings, and they are strongly

radiatively cooled.

A large number of studies have reported the dynamical evolution of such

jets: cooling results in the formation of thin dense shells which are easily

fragmented into clumps and "bullets".