Demonstrations
Rubens' Tube
A length of pipe is perforated along the top and sealed at both ends - one seal is attached to a small speaker or frequency generator, the other to a supply of a flammable gas (propane tank). The pipe is filled with the gas, and the gas leaking from the perforations is lit. If a suitable constant frequency is used, a standing wave can form within the tube. When the speaker is turned on, the standing wave will create points with oscillating (higher and lower) pressure and points with constant pressure (pressure nodes) along the tube. Where there is oscillating pressure due to the sound waves, less gas will escape from the perforations in the tube, and the flames will be lower at those points. At the pressure nodes, the flames are higher. At the end of the tube gas molecule velocity is zero and oscillating pressure is maximal, thus low flames are observed. It is possible to determine the wavelength from the flame minima and maxima by simply measuring with a ruler.
Since the time averaged pressure is equal at all points of the tube, it is not straightforward to explain the different flame heights. The flame height is proportional to the gas flow as shown in the videos. Based on Bernoulli’s principle, the gas flow is proportional to the square root of the pressure difference between the inside and outside of the tube. This is shown in the videos for a tube without standing sound wave. Based on this argument, the flame height depends non-linearly on the local, time-dependent pressure. The time average of the flow is reduced at the points with oscillating pressure and thus flames are lower.
By Dany Huot & Vorleak Ban
How to make Rubens' Tube
Rubens' Tube - Sound waves at various frequencies
Rubens' Tube - Collection Of Songs
Rubens' Tube - Sertab Erener - Everyway That I Can
Rubens' Tube - Destiny's Child - Story Of Beauty
Rubens' Tube - Hector El Fago - Rumba
Rubens' Tube - Queen - We Will Rock You
Rubens' Tube - Sean Paul - Can You Do The Work
Rubens' Tube - Shakira - Eyes Like Yours - Ojos Asi
Rubens' Tube - Photos
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