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Dopplerby Raparicio
Tags: doppler 
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#1
May2505, 06:08 PM

P: 112

Hello,
There's a problem with the doppler efect that I don't understand. When a object runs at a velocity a little minor than velocity of sound, appears in front of the emisor a group of high frecuence, that in simulators (applets) is increasing in time. This wave, is like a physical object, that acts like a wall? In the exactly case that the object goes at mach 1, how can we calculate the doppler efect? in theory, there's a wave of infinite frecuency and power (???) 


#2
May2505, 11:41 PM

P: 542

Doppler's effect is not applicable to ultrasonic sounds. Thats for your second one.Please clarify the first question....a bit corrugated..



#3
May2605, 11:28 AM

P: 112

Dear Dr. Brain,
Thanks for the first. The second question is, how can we calculate the waves that are generated at the exactly velocity velocity of sound. In this, we see that waves are acumulated in front of the moving object, but in the clasical formulas it's a mathematical singularity. best reggards. 


#4
May2605, 01:02 PM

Sci Advisor
HW Helper
P: 3,033

Doppler
http://antwrp.gsfc.nasa.gov/apod/ap010221.html When the source is moving at the speed of sound or greater, there is a shock wave produced that is modeled by the applets you refer to. The shock wave is not a simple sinusoidally varying waveform. It is a highly energetic wavefront of a large change in air pressure that is heard as a "sonic boom". It's frequency spectrum is much more complex than the frequency of the source, and cannot be determined from simple doppler considertions. When it arrives, it shakes buildings and rattles windows. After the initial shock passes, the ususal sound waves arrive with frequncy components determined by the doppler effect. Of course when those waves arrive at an observer, the object that produced the sound has long since moved away from where that sound was produced. Even at subsonic speeds you can often see a jet in the sky and hear the sound coming from a point far behind it. Try this http://faculty.rmwc.edu/tmichalik/movies/F18.MPEG If that doesn't work try going to this site to download it http://faculty.rmwc.edu/tmichalik/physmov.htm 


#5
May2605, 01:45 PM

P: 112

Dear OlderDan,
Thanks for your dedication to this question. This information is very interesting and just what I'm looking for. You say: "as Mach 1 is approached there is a very real and highly energetic disturbance in the atmosphere that does serve as a "barrier" that must be penetrated to achieve higher speeds." Id like to calculate it numerically. It exists information about this wave, its formulation, characteristics, etc? Thanks for all. R. Aparicio. 


#6
May2605, 02:17 PM

Sci Advisor
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P: 3,033

http://www.fas.org/sgp/othergov/doe/...s/00326956.pdf 


#7
May2605, 02:17 PM

P: 542

Perhaps , you would like to know about the Cherenkov Radiation that is emitted when an onject reaches Mach1 speed. Google the term for more information .



#8
May2605, 02:19 PM

P: 542

Perhaps , you would like to know about the Cherenkov Radiation that is emitted when an object reaches Mach1 speed. Google the term for more information .



#9
May2605, 06:36 PM

P: 112

Really, your information has been very useful to me.
I've found that the equation of Rankinehugoniot is that works with it. Now the problem is to find information about this. Thanks to all. R. Aparicio. 


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