Rijke tube
Encyclopedia
Rijke's tube 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
.
was a professor
of physics
at the Leiden University
in the Netherlands
when, in 1859, he discovered a way of using heat to sustain a sound in a cylindrical
tube open at both ends. He used a glass
tube, about 0.8 m long and 3.5 cm in diameter. Inside it, about 20 cm from one end, he placed a disc of wire gauze as shown in the figure below. Friction
with the walls of the tube is sufficient to keep the gauze in position. With the tube vertical and the gauze in the lower half, he heated the gauze with a flame
until it was glowing red hot. Upon removing the flame, he obtained a loud sound from the tube which lasted until the gauze cooled down (about 10 s
). It is safer in modern reproductions of this experiment to use a Pyrex
tube or, better still, one made of metal
.
Instead of heating the gauze with a flame, Rijke also tried electrical
heating. Making the gauze with electrical resistance wire
causes it to glow red when a sufficiently large current is passed. With the heat being continuously supplied, the sound is also continuous and rather loud. Rijke seems to have received complaints from his university colleagues because he reports that the sound could be easily heard three rooms away from his laboratory. The electrical power required to achieve this is about 1 kW.
Lord Rayleigh, who wrote the definitive textbook on sound in 1877, recommends this as a very effective lecture
demonstration. He used a cast iron
pipe 1.5 m long and 12 cm diameter with two layers of gauze made from iron
wire inserted about quarter of the way up the tube. The extra gauze is to retain more heat, which makes the sound longer lasting. He reports in his book that the sound rises to such intensity as to shake the room!
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 and subsequently investigated by German physicist Peter Theophil Rieß.
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. 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 pressure
reaches a maximum. During the other half cycle, the flow of air is outwards until the minimum pressure is reached. All air flowing past the gauze is heat
ed to the temperature of the gauze and any transfer of heat to the air will increase its pressure according to the gas law.
As the air flows upwards past the gauze most of it will already be hot because it has just come downwards past the gauze during the previous half cycle. However, just before the pressure maximum, a small quantity of cool air comes into contact with the gauze and its pressure is suddenly increased. This increases the pressure maximum, so reinforcing the vibration. During the other half cycle, when the pressure is decreasing, the air above the gauze is forced downwards past the gauze again. Since it is already hot, no pressure change due to the gauze takes place, since there is no transfer of heat. The sound wave is therefore reinforced once every vibration cycle and it quickly builds up to a very large amplitude
.
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 engine
s" or "prime movers".
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 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.
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. (In demonstration models, the tube can be heated externally and steel wool can serve as a stack.)
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
into sound
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
, by creating a self-amplifying standing wave
Standing wave
In physics, a standing wave – also known as a stationary wave – is a wave that remains in a constant position.This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling...
. It is an entertaining phenomenon in acoustics
Acoustics
Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...
and is an excellent example of resonance
Resonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
.
Discovery
P. L. RijkePieter Rijke
Petrus Leonardus Rijke was a Dutch physicist, and a professor in experimental physics at the University of Leiden. Rijke spent his scientific career exploring the physics of electricity, and is known for the Rijke tube.On July 1, 1852 he was married to Johanna Hamaker...
was a professor
Professor
A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...
of physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
at the Leiden University
Leiden University
Leiden University , located in the city of Leiden, is the oldest university in the Netherlands. The university was founded in 1575 by William, Prince of Orange, leader of the Dutch Revolt in the Eighty Years' War. The royal Dutch House of Orange-Nassau and Leiden University still have a close...
in the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
when, in 1859, he discovered a way of using heat to sustain a sound in a cylindrical
Cylinder (geometry)
A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...
tube open at both ends. He used a glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
tube, about 0.8 m long and 3.5 cm in diameter. Inside it, about 20 cm from one end, he placed a disc of wire gauze as shown in the figure below. Friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
with the walls of the tube is sufficient to keep the gauze in position. With the tube vertical and the gauze in the lower half, he heated the gauze with a flame
Flame
A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...
until it was glowing red hot. Upon removing the flame, he obtained a loud sound from the tube which lasted until the gauze cooled down (about 10 s
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
). It is safer in modern reproductions of this experiment to use a Pyrex
Pyrex
Pyrex is a brand name for glassware, introduced by Corning Incorporated in 1915.Originally, Pyrex was made from borosilicate glass. In the 1940s the composition was changed for some products to tempered soda-lime glass, which is the most common form of glass used in glass bakeware in the US and has...
tube or, better still, one made of metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
.
Instead of heating the gauze with a flame, Rijke also tried electrical
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...
heating. Making the gauze with electrical resistance wire
Resistance wire
Resistance wire is electrical wire used for its property of electrical resistance. It is routinely used at high temperatures, so normally also has high melting point....
causes it to glow red when a sufficiently large current is passed. With the heat being continuously supplied, the sound is also continuous and rather loud. Rijke seems to have received complaints from his university colleagues because he reports that the sound could be easily heard three rooms away from his laboratory. The electrical power required to achieve this is about 1 kW.
Lord Rayleigh, who wrote the definitive textbook on sound in 1877, recommends this as a very effective lecture
Lecture
thumb|A lecture on [[linear algebra]] at the [[Helsinki University of Technology]]A lecture is an oral presentation intended to present information or teach people about a particular subject, for example by a university or college teacher. Lectures are used to convey critical information, history,...
demonstration. He used a cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...
pipe 1.5 m long and 12 cm diameter with two layers of gauze made from iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
wire inserted about quarter of the way up the tube. The extra gauze is to retain more heat, which makes the sound longer lasting. He reports in his book that the sound rises to such intensity as to shake the room!
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 and subsequently investigated by German physicist Peter Theophil Rieß.
Mechanism
The sound comes from a standing waveStanding wave
In physics, a standing wave – also known as a stationary wave – is a wave that remains in a constant position.This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling...
whose wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
is about twice the length of the tube, giving the fundamental frequency
Fundamental frequency
The fundamental frequency, often referred to simply as the fundamental and abbreviated f0, is defined as the lowest frequency of a periodic waveform. In terms of a superposition of sinusoids The fundamental frequency, often referred to simply as the fundamental and abbreviated f0, is defined as the...
. Lord Rayleigh, in his book, gave the correct explanation of how the sound is stimulated. 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
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
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 pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
reaches a maximum. During the other half cycle, the flow of air is outwards until the minimum pressure is reached. All air flowing past the gauze is heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
ed to the temperature of the gauze and any transfer of heat to the air will increase its pressure according to the gas law.
As the air flows upwards past the gauze most of it will already be hot because it has just come downwards past the gauze during the previous half cycle. However, just before the pressure maximum, a small quantity of cool air comes into contact with the gauze and its pressure is suddenly increased. This increases the pressure maximum, so reinforcing the vibration. During the other half cycle, when the pressure is decreasing, the air above the gauze is forced downwards past the gauze again. Since it is already hot, no pressure change due to the gauze takes place, since there is no transfer of heat. The sound wave is therefore reinforced once every vibration cycle and it quickly builds up to a very large amplitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
.
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
Thermoacoustics
Thermoacoustics is about the interaction between thermodynamic and acoustic phenomena. Thermoacoustics is a relatively new field of science and engineering. Few devices based on this principle have been made thus far...
devices known as "heat engine
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...
s" 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). Lord Rayleigh first explained the operation of the Sondhauss tube.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 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.
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. (In demonstration models, the tube can be heated externally and steel wool can serve as a stack.)
Further information
- K. T. Feldman, Jr. (1968) "Review of literature on Rijke thermoacoustic phenomena," Journal of Sound and Vibration, vol. 7, no. 1, pages 83–89.
- In German: Rijke-Rohr [Rijke tube]: http://wundersamessammelsurium.info/akustisches/rijke_rohr/index.html . Includes links to original articles by Rijke, Riess, etc.
- R. E. Evans and A. A. Putnam (1966) "Rijke Tube Apparatus," American Journal of Physics, vol. 34, no. 4, pages 360-361.