• Created by Unknown User (albertog), last modified on 10.12.2012

You are viewing an old version of this page. View the current version.

Compare with Current View Page History

« Previous Version 32 Next »

Short description


Reference 1: http://physics.info/shock/


A shockwave is high pressure wave produced by an object that travels faster than the speed of sound according to the same medium characteristics, in which different changes can be measured for example; extreme pressure and rising of the temperature.

The visualisation of the shockwave can be seen in the following picture.

History

historia por francisto.....



Shockwave

As an object moves through a gas, the gas molecules are deflected around the object. If the speed of the object is much less than the speed of sound of the gas, the density of the gas remains constant and the flow of gas can be described by conserving momentum and energy. As the speed of the object increases towards the speed of sound, we must consider compressibility effects on the gas. The density of the gas varies locally as the gas is compressed by the object

 Extracorporeal shock wave lithotripsy (ESWL) is one of the well-known applications of shock waves. In addition to this success, , shock waves are applied to treat cancer, orthopaedic surgery in recent years. In brain neuro-surgery a revasculariztion of cerebral thrombosis is going to be established. Many interesting problems remained unresolved and its further improvements are required in order to achieve successful clinical applications

Why Shock wave happens

When the speed of a source exceeds the speed of sound (v > c) the wave fronts lag behind the source in a cone-shaped region with the source at the vertex. The edge of the cone forms a supersonic wave front with an unusual large amplitude called a "shock wave". When a shock wave reaches an observer a "sonic boom" is heard.

Unlike ordinary sound waves, the speed of a shock wave varies with its amplitude. The speed of a shock wave is always greater than the speed of sound in the fluid and decreases as the amplitude of the wave decreases. When the shock wave speed equals the normal speed, the shock wave dies and is reduced to an ordinary sound wave.

    
Reference 2: http://www.grc.nasa..../machang.html





       

In case that:

C = Speed of sound
V = Speed of the moving object
M = Mach number (Would be M)

So if an object move twice time faster that sound speed the Mach number would 2.


When an object travels slower than sound, the ratio in this equation is greater than one, and the equation does not have a real solution. Traveling at the speed of sound makes the ratio equal one and results in a Mach angle of ninety degrees. Above the speed of sound, the ratio is less than one and the Mach angle is less than ninety degrees. The faster the object moves, the narrower the cone of high pressure behind it becomes. Measuring the vertex angle is a way to determine the speed of a supersonic object.


Reference 3: Screenshots from the Video bellow.

Mach Number


Reference 4: http://www.grc.nasa./airplane/mach.html

This number was proposed by the Austrian phycisist and philosofer Ernst Mach in (1838-1916), one of the most notorius teorist phisicist.
The mach number is known as a measurement  or unit and is defined as the coeficient of the velocity of an object and the velocity of the sound.

This number is used to express the velocity of an object taking the sound velocity as a reference, something very interesting about the moment is that velocity of sound changes depending on the atmospheric conditions.

For example: With a higher altitude compare to the sea level, the speed of sound is less than the one found at the sea level.

Video

References

Reference 1: http://physics.info/shock/

Reference 2: http://www.grc.nasa.gov/WWW/k-12/airplane/machang.html

Reference 3: Screenshot from the video bellow.

Reference 4: http://www.grc.nasa.gov/WWW/k-12/airplane/mach.html

Video 1: https://www.youtube.com/watch?v=gWGLAAY

  • No labels
You must log in to comment.