Why does turbulence develop, after some distance is travelled by a 'calm' water stream?

Question

I am asking this question considering the phenomenon observed in the stream pouring out of a faucet (supposing it doesn't have an aerator).

While answering please take into account that I'm not very well versed in Fluid dynamics.
I would prefer answers without equations!

Answer 1

The transition from laminar (smooth) fluid flow to turbulent (irregular, unpredictable) flow is chiefly a function of a key parameter called the Reynolds number.

The Reynolds number increases as...
1. the fluid velocity increases
2. the size of the system increases
3. the density of the fluid increases
4. the viscosity of the fluid decreases

For a given geometry (such as a cylindrical pipe), there is a certain critical Reynolds number. Below this number, the system will tend to settle into laminar flow. As you increase the fluid velocity, the Reynolds number increases. When you exceed the critical number, the flow will become random and unpredictable, swirling in complex, three-dimensional patterns.

The situation is even more complex for free-falling water, however, there is one thing in common. As the water falls, it accelerates. Higher velocity means higher Reynolds number. At some point, it exceeds the critical value and becomes turbulent. However, unlike the pipe scenario, instead of simply forming random swirls, the turbulence eventually breaks the entire stream into pieces, and surface tension pulls the globs of water into round shapes. If you let the water fall far enough, you will end up with small droplets instead of a steady stream.

Answer 2

Look at it this way. First imagine a perfect stream of water. All the water is moving in the same direction at the same speed. Now a foot away from the source of the stream you add some random disturbance, another foot away there is another disturbance, etc. Obviously these disturbances will add slight variations to the flow, the farther the water has travel the more random variation there will be. Eventually the amount and magnitude of these variations will be so large that they significant alter the water stream. This is exactly how turbulence forms. There are any number of random variations affecting any stream of water (sounds, pipe roughness, slight temperature differences,etc). The further the steam travels the more these variations will grow.

Answer 3

K, scared of air plane crashes or plunging to the open water and freezing to death cause of hypothermia or it crashing and burning. Well, think of this. How manycar crashess happen in a year. Twice-hundred-million? How manyair planee crashes in a year. Once- Twice. Not even. And turbulence is a normal thing. Just hot air coming up. No need to worry.

Answer 4

A stream speeds up when it is confined to a narrower or shallower channel or when the slope of the channel becomes steaper. The roughness of the channel boundaries also contributes to turbulence.