Falling stream of water > individual droplets

In summary, a falling stream of water breaks into individual droplets due to surface tension and air resistance. Some droplets may appear to merge back together due to coalescence. The shape and size of the nozzle or source of the water can affect the formation of droplets, and gravity plays a crucial role in their formation. Understanding this process has practical applications in industries such as agriculture, inkjet printing, and spray coating.
  • #1
ab500
1
0
Hi,

I'm looking at finding a way to determine when a stream of water of a certian diameter coming from a hole at a certian pressure will break apart due to gravity and surface tension into descrete droplets.

Bernoulli's principle can give me the diameter of the stream at various times but I don't know what exactly governs the breaking apart of the stream into droplets.

Any help?
 
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  • #2
Look into "Rayleigh instability."
 
  • #3
This problem (jet dynamics) is very old, and a definitive presentation is in Chandrasekhar's book "hydrodynamic and hydromagnetic stability" (Dover). Surface tension drives the jet breakup.
 

1. How does a falling stream of water break into individual droplets?

When a continuous stream of water falls from a height, it experiences surface tension, which causes it to maintain its shape. However, as it falls, it encounters air resistance, which starts to break the stream into smaller droplets. The size and frequency of these droplets depend on various factors such as the speed and volume of the falling water, as well as the surface tension and viscosity of the water itself.

2. Why do some droplets from a falling stream appear to merge back together?

This phenomenon is known as coalescence, and it occurs due to the surface tension of the water. As the smaller droplets fall through the air, they encounter air resistance, which causes them to slow down. This allows the water molecules on the surface of the droplets to move closer together, eventually merging them back into a larger droplet.

3. Can the shape of the nozzle or source of the falling water affect the formation of individual droplets?

Yes, the shape and size of the nozzle or source of the water can greatly impact the formation of individual droplets. For example, a narrow nozzle will produce a more focused stream, resulting in smaller and more frequent droplets. On the other hand, a wider nozzle will produce a wider stream with larger and less frequent droplets.

4. How does gravity play a role in the formation of individual droplets?

Gravity is a crucial factor in the formation of individual droplets. As the water falls, it experiences the force of gravity, which pulls it downwards. This force also helps to break the stream into smaller droplets, as the larger droplet cannot withstand the force and breaks apart. Gravity also determines the speed at which the droplets fall, which can impact their size and frequency.

5. Are there any practical applications for understanding the formation of individual droplets from a falling stream of water?

Yes, understanding the formation of individual droplets from a falling stream of water has several practical applications. It is essential in industries such as agriculture, where the size and frequency of droplets can impact the effectiveness of irrigation systems. It is also crucial in fields such as inkjet printing and spray coating, where the formation of individual droplets is necessary for precise and consistent results.

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