the joy of fountains !!

For Chennaites, it was a great respite from hot weather .. .. yesterday it rained !  .. .. and water could be seen on roads.  In the evening casual walkers of Marina beach enjoyed the fountain nearer Gandhi statue .. .. 

‘what you see with your eyes  – may  not be truly what it is !’ – Water fountain sprinkles water all around – looks so nice – as water rises and falls in an arc !  but when photographed, they seemingly are individual particles.  

For those who are good in Maths – what will be the total area around the fountain that gets wet – and what would be parameters required to calculate this – the speed of the water & … .. ……. 

A fountain, from the Latin "fons" (genitive "fontis"), meaning source or spring, is a decorative reservoir used for discharging water. It is also a structure that jets water into the air for a decorative or dramatic effect. Fountains were originally purely functional, connected to springs or aqueducts and used to provide drinking water and water for bathing and washing to the residents of cities, towns and villages. Until the late 19th century most fountains operated by gravity, and needed a source of water higher than the fountain, such as a reservoir or aqueduct, to make the water flow or jet into the air. 

Read that there is :  Bernoulli's principle? [obviously I could not understand and make out what it is].  Bernoulli's principle is a seemingly counterintuitive statement about how the speed of a fluid relates to the pressure of the fluid.    Bernoulli's principle: Within a horizontal flow of fluid, points of higher fluid speed will have less pressure than points of slower fluid speed.  So within a horizontal water pipe that changes diameter, regions where the water is moving fast will be under less pressure than regions where the water is moving slow.   

Among many other things, Rome is notable as a city of fountains. This is, in some sense, an indirect result of the physics of arches  available there. The acqueducts constructed by the Roman emperors brought so much water to the city from distant mountains that they were more than able to meet the need for drinking water and public baths. Which allowed the construction of fountains in private villas and public squares. 

The rulers who came in later, continued and expanded this idea, leading to monumental masterworks of public art like Gian Lorenzo Bernini's Fontana dei Quattro Fiumi in the Piazza Navona and Nicola Salvi's iconic Trevi Fountain. The latter is so famous it can be difficult to photograph for the crush of selfie-snapping tourists!!  -writes Forbes.  The appeal of public fountains goes beyond the work of the sculptors who design and carve them, though, with the water playing a critical role in the aesthetic appeal. 

The author adds : - the Piazza del Popolo in Rome- the  stream of water exits the lion's mouth as a wide continuous jet, but after some distance, the smooth sheet of water breaks up into smaller droplets. This breaking-up process leads to both of the pleasing effects of water in fountains: the pattern of breaking shifts randomly from one instant to the next, providing an ever-changing visual pattern, and that same randomness ensures that the drops splash into the basin with no particular pattern, making the pleasant "white noise" sound we associate with fountains. 

This beautiful break-up has a kind of ugly technical name in physics: it's the result of the "Plateau–Rayleigh instability".  The ultimate cause of this, though, has to do with microscopic interactions between the molecules making up the flow of water. At the surface, though, any given molecule is only half surrounded by other molecules of water. Which destroys the balance we find in the middle of the liquid, and leaves a net force pulling in toward the center of the liquid. This "surface tension" is what gives water its internal cohesion. The surface is pulled in until those molecules start to run into other molecules, which leads to an outward pressure. In the absence of any other interactions, the balance between the inward pull and outward push will shape a water drop into a sphere. 

Water being a liquid, though, a difference in pressure will cause molecules to move from high pressure to low. Which will tend to take liquid away from thin spots, making them still thinner, while thick spots get thicker.   

I am not able to understand the Science behind and the  concept, yet, it was an interesting spectacle.

With regards – S. Sampathkumar
11.5.2022