Rijke tube
The Rijke tube is a cylindrical tube with both ends open, inside of which a heat source is placed that turns heat into sound, by creating a self-amplifying standing wave. It is an entertaining phenomenon in acoustics and is an excellent example of resonance.
Discovery
Instead of heating the gauze with a flame, Rijke also tried
A "reverse" Rijke effect — namely, that a Rijke tube will also produce audio oscillations if hot air flows through a cold screen — was first observed by Rijke's assistant Johannes Bosscha[3] and subsequently investigated by German physicist Peter Theophil Rieß.[4][5][6]
Mechanism
The sound comes from a standing wave whose wavelength is about twice the length of the tube, giving the fundamental frequency. Lord Rayleigh, in his book, gave the correct explanation of how the sound is stimulated.[7] The flow of air past the gauze is a combination of two motions. There is a uniform upwards motion of the air due to a convection current resulting from the gauze heating up the air. Superimposed on this is the motion due to the sound wave.
For half the vibration cycle, the air flows into the tube from both ends until the
This explains why there is no sound when the flame is heating the gauze: all air flowing through the tube is heated by the flame, so when it reaches the gauze, it is already hot and no pressure increase takes place.
When the gauze is in the upper half of the tube, there is no sound. In this case, the cool air brought in from the bottom by the convection current reaches the gauze towards the end of the outward vibration movement. This is immediately before the pressure minimum, so a sudden increase in pressure due to the heat transfer tends to cancel out the sound wave instead of reinforcing it.
The position of the gauze in the tube is not critical as long as it is in the lower half. To work out its best position, there are two things to consider. Most heat will be transferred to the air where the displacement of the wave is a maximum, i.e. at the end of the tube. However, the effect of increasing the pressure is greatest where there is the greatest pressure variation, i.e. in the middle of the tube. Placing the gauze midway between these two positions (one quarter of the way in from the bottom end) is a simple way to come close to the optimal placement.
The Rijke tube is considered to be a standing wave form of thermoacoustic devices known as "heat engines" or "prime movers".
Sondhauss tube
The Rijke tube operates with both ends open. However, a tube with one end closed will also generate sound from heat, if the closed end is very hot. Such a device is called a "Sondhauss tube". The phenomenon was first observed by glassblowers and was first described in 1850 by the German physicist Karl Friedrich Julius Sondhauss (1815–1886).[8][9] Lord Rayleigh first explained the operation of the Sondhauss tube.[10]
The Sondhauss tube operates in a way that is basically similar to the Rijke tube: Initially, air moves towards the hot, closed end of the tube, where it's heated, so that the pressure at that end increases. The hot, higher-pressure air then flows from the closed end towards the cooler, open end of the tube. The air transfers its heat to the tube and cools. The air surges slightly beyond the open end of the tube, briefly compressing the atmosphere; the compression propagates through the atmosphere as a sound wave. The atmosphere then pushes the air back into the tube, and the cycle repeats. Unlike the Rijke tube, the Sondhauss tube does not require a steady flow of air through it, and whereas the Rijke tube acts as a half-wave resonator, the Sondhauss tube acts as a quarter-wave resonator.[11]
Like the Rijke tube, it was discovered that placing a porous heater — as well as a "stack" (a "plug" that is porous) — in the tube greatly increased the power and efficiency of the Sondhauss tube.[12][13] (In demonstration models, the tube can be heated externally and steel wool can serve as a stack.)[14]
See also
References
- . [modern citation: Annalen der Physik, 183: 339–343].
- ^ Strutt, John Wm. (Lord Rayleigh) (1879). "Acoustical observations". Philosophical Magazine. 5th series. 7: 149–162.
- .
- .
- .
- ^ Lord Rayleigh mentions the discoveries of Bosscha and of Riess in: Strutt, John Wm. (Baron Rayleigh) (1896). The Theory of Sound. Vol. 2 (2nd ed.). London, England, U.K.: Macmillan. pp. 233–234. ; reprinted by Dover Publications (New York, New York, USA) in 1945.
- S2CID 4140025. See also: Strutt, John Wm. (Baron Rayleigh) (1896). The Theory of Sound. Vol. 2 (2nd ed.). London, England, U.K.: Macmillan. pp. 231–234. ; reprinted by Dover Publications (New York, New York, USA) in 1945.
- ^ Sondhauss, Karl (1850). "Über die Schallschwingungen der Luft in erhitzten Glasrohren und in gedeckten Pfeifen von ungleicher Weite" [On acoustic oscillations of the air in heated glass tubes and in closed pipes of non-uniform width]. Annalen der Physik und Chemie. 2nd series (in German). 79: 1–34.
- ^ Many sources spell "Karl Sondhauss" as "Carl Sondhaus" or "Carl Sondhauss".
- ^ Strutt, John Wm. (Baron Rayleigh) (1896). The Theory of Sound. Vol. 2 (2nd ed.). London, England, U.K.: Macmillan. pp. 230–231. ; reprinted by Dover Publications (New York, New York, USA) in 1945.
- ISBN 9780387304465.
- ^ Heat exchangers were first placed in Sondhauss tubes by Carter, White and Steele: Robert Leroy Carter, M. White, and A.M. Steele (1962) Private communication, Atomics International Division of North American Aviation, Inc. The first published account of stacks in Sondhauss tubes was by Karl Thomas Feldman, Jr. See:
- Feldman, K. T. (1966) "A study of heat generated pressure oscillations in a closed end pipe," Ph.D. dissertation, Mechanical Engineering Department, University of Missouri.
- Feldman, K. T. Jr.; Hirsch, H.; Carter, R. L. (June 1966). "Experiments on the Sondhauss thermoacoustical phenomenon". Journal of the Acoustical Society of America. 39 (6): 1236.
- Feldman, K. T. Jr. (January 1968). "Review of the literature on Sondhauss thermoacoustic phenomenon". Journal of Sound and Vibration. 7 (1): 71–82. .
- Feldman, K. T. Jr.; Carter, R. L. (1970). "A study of heat driven pressure oscillations in a gas". Journal of Heat Transfer. 92 (3): 536–541. . See also:
- Wheatley, J. C.; Hofler, T.; Swift, G. W.; Migliori, A. (1985). "Understanding some simple phenomena in thermoacoustics with applications to acoustical heat engines". American Journal of Physics. 53 (2): 147–162. doi:10.1119/1.14100.
- The description of the "acoustic laser" in: Garrett, Steven; Backhaus, Scott (November–December 2000). "The power of sound" (PDF). American Scientist. 88 (6): 516–525. .
- Scott Backhaus and Greg Swift, "New varieties of thermoacoustic engines," 9th International Congress on Sound and Vibration (Orlando, Florida, USA), July 2002.
- A technical analysis of this quarter-wave, standing-wave "engine" is presented in: Swift, Greg (2007). "Chapter 7: Thermoacoustics". In Rossing, Thomas (ed.). Springer Handbook of Acoustics. New York, New York, USA: Springer. pp. 241 and 244–246. ISBN 9780387304465.
- Thermoacoustic hot air engine.
- ^ On YouTube, see for example:
Further information
- Feldman, K.T. Jr. (1968). "Review of literature on Rijke thermoacoustic phenomena". Journal of Sound and Vibration. 7 (10): 83–89. .
- Rijke-Rohr (Rijke tube) at: Wundersames Sammelsurium (Wondrous Collection) (in German) Includes original articles by early investigators of thermoacoustics (Rijke, Reiss, etc.).
- Evans, R. E.; Putnam, A. A. (1966). "Rijke tube apparatus". American Journal of Physics. 34 (4): 360–361. .
- Julius Sumner Miller, "Sounding Pipes" on YouTube Demonstrations of Rijke tubes.