hollywoodtone.blogspot.com What makes a kettle whistle?
hollywoodtone.blogspot.com What makes a kettle whistle?
What causes the sound when the water in a kettle on a hob boils and turns to steam? The answer in many physics text books might be wrong, according to a study.
The traditional answer to the question ‘why does a kettle whistle’ dates back to British physicist Lord Rayleigh. Rayleigh proposed in 1877 that water molecules bouncing back and forth in the spout produce the whistle. However, a new study suggests that swirls of steam are responsible. This comes from a study conducted at the University of Cambridge. With the new study, engineers mimicked a tea kettle in the laboratory using tubing and a series of pressure sensors and microphones. The researchers found a two-step process: steam lazily rising from water that is just starting to boil vibrates within the spout to produce a faint tone, much the way a bottle neck hums when you blow across its mouth. Then, as pressure builds and a strong jet of steam escapes through the lid’s opening, small vortices of steam break off and create pressure waves in the air. This takes the form of a high-pitched whistle. The whistle rises in pitch as the speed of the jet grows. This finding has been reported in the journal Physics of Fluids. The paper is titled “The aeroacoustics of a steam kettle”. As to the original Lord Rayleigh he still has a number of considerable achievements to his name, so if he was incorrect about the kettle whistle it won't detract too much from his historical standing. Lord Rayleigh (otherwise known as John William Strutt, 3rd Baron Rayleigh) was an English physicist who, with William Ramsay, discovered argon, an achievement for which he earned the Nobel Prize for Physics in 1904. He also discovered the phenomenon now called Rayleigh scattering, explaining why the sky is blue, and predicted the existence of the surface waves now known as Rayleigh waves.
hollywoodtone.blogspot.com What makes a kettle whistle?