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Why does water fall in a twisted shape, when it comes from the hose or bottle? It can be seen when you are watering the flowers from a can.

And the measure of the twisted depends on what (for example the speed of the out-coming water)?

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  • $\begingroup$ You have not provided any visual evidence of the effect you are asking about, nor any links to evidence. I can find few online images showing a twisting spiral - this is closest but includes no explanation of the conditions... Without such evidence, it is difficult to know exactly what effect you are asking about. count_to_10 assumes it is caused by a Coriolis Force, but there are other explanations, eg relating to instabilities. $\endgroup$ – sammy gerbil Aug 26 '16 at 23:31
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Why does water fall in a twisted shape, when it comes from the hose or bottle? It can be seen when you are watering the flowers from a can.

As you picked up the bottle of liquid, the sloshing of the liquid inside may impart angular momentum to it. In order to preserve this angular momentum, the liquid emerging will speed up and tighten its spral motion.

In other situations, the corkscrew / twisting effect you may notice is the bottom end of the whirlpool that is occurring inside the container as the liquid emerges may be due to the Coriolis Force .

enter image description here

In the inertial frame of reference (upper part of the picture), the black ball moves in a straight line. However, the observer (red dot) who is standing in the rotating/non-inertial frame of reference (lower part of the picture) sees the object as following a curved path due to the Coriolis and centrifugal forces present in this frame.

 

enter image description here

Image source: Swirling Water

It's not only bottles or water hoses that produces the spral shape shown in the picture above, you get the same phenomenon occurring in square or rectangular juice containers, but because the opening of these cardboard based packets are different, you may not notice it.

Squeeze the plastic bottle the next time you pour water and see does the effect become more evident. By squeezing the bottle, even just by holding it so it won't fall, you increase the velocity of the liquid, which increases the Coriolis force, which is proportional to the speed of an object in a rotating inertial frame, in addition to the rotational velocity and the distance from the object to the axis of rotation.

Another reason for the twisting of water is simply the shape of the hole the liquid emerges from, along with surface tension forces and pressure differences across the width of the hole the liquid is poured from.

This second reason has nothing to do with the Coriolis effect, but does explain say, water hoses producing the same swirling effect.

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