Short description
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Reference 1: http://www.physics.info/shock/
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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.
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History
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Reference 2: http://www.nasa/...2.pdf
| Rankine, was the first relevant figure who developed the theory, he makes his main contribution in his 1870 paper on the thermodynamic theory of waves published in the Philosophical Transactions of the Royal Society of London.
- He begins with: “The object of the present investigation is to determine the relations which must exist between the laws of the elasticity of any substance, whether gaseous, liquid, or solid, and those of the wave-like propagation of a finite longitudinal disturbance in that substance.”
- Later he writes: “It is to be observed, in the first place, that no substance yet known fulfills the condition expressed by the equation  , between finite limits of disturbance, at a constant temperature, nor in a permanency of type may be possible in a wave of longitudinal disturbance there must be both change of temperature and conduction of heat during the disturbance”.
Therefore, Rankine by explaining that the shock transition is a non-adiabatic process, where the particles exchange heat with each other, but no heat is received from the outside, resolved the objections that had been raised by Rayleigh and others concerning the conservation of energy.
He goes on to find, for a perfect gas, the jump conditions for a shock wave moving with speed a into an undisturbed medium with pressure and specific volume defined respectively by P and S. |
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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:http3: //www.grc.nasa..../machang.html |
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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 34: Screenshots from the Video bellow.
Mach Number
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Reference 45: http://www.nasa.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. |
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Reference 1: http://physics.info/shock/
Reference 2: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060047586_2006228914.pdf
Reference 23: http://www.grc.nasa.gov/WWW/k-12/airplane/machang.html
Reference 34: Screenshot from the video bellow.
Reference 45: http://www.grc.nasa.gov/WWW/k-12/airplane/mach.html
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