I guess its because of a pressure difference as created by sound, as at one place there is compression and at another place there is expansion. Water prefers to go in lower pressure so while going forward it bends towards lower pressure. It happen at lower frequency because water have enough time to respond. For all this to imagine, just see at pipe , pipe will go forward and then backward , maybe its due to at one time there is low pressure at one place , then at place where there is low pressure , then it is shifted by high pressure , and pipe move forward so pipe could go at place where there is low pressure .may be its happening to every part , but why it is rotating ? Does anyone have an idea why it is happening?
https://twitter.com/thebestofgifs1/status/526444950401998848
see this for viewing pic.
Edit: Not going to make pipe oscillate , because
1)24hz is still large frequency and hence very less time period in order to whole pipe react.
2) The force applied by that pressure is very less , so whole pipe is not going to move .
We can do little bit of maths to proof it .. so this idea which is given above is wrong.
The video is a trick of video photography. There is nothing special going on in the physics of fluid motion. And nothing in terms of sound-flow interaction.
Note that the title of the video expressly points out that the frame-rate of the video camera (24 Hz) is exactly the same as the vibration (24 Hz). They are calling vibrations sound. 25 Hz is usually considered to be the lowest sound-frequency perceptible to very carefully attentive people, so the vibrations are infrasonic.
In any case, presumably the nozzle out of which the water flows is in significant rotational motion at 24 Hz. The trick of video-photography is that we only see the nozzle at the instant that it has returned to the same position after one rotation. This is because the nozzle motion and the video frame-rate are matched. The nozzle appears to be nearly stationary in the video, but it is actually moving significantly.
It is rather the same video trick that happens when watching a wheel rotate on a car advertisement on television. As the car accelerates away from stopped position, the car eventually reaches a speed where the wheels appear to stop rotating in the advertisement, and sometimes appear to be rotating in reverse as the car moves forward. That is because the video frame rate matches the rate of wheel rotation (wheels apparently stop), or is somewhat greater (or is it less?) than the rate of wheel rotation (wheel apparently turns in reverse). The wheels are of course rotating normally, and uninterestingly.
In the case of the neat video with the water, the matched frame rate of the camera ensures that we are seeing the nozzle and the falling water at precisely the instants required to give the visual illusion of water from a still nozzle spiraling with properties that apparently defy fluid dynamics. If you filmed it all with a very much faster frame rate, then it would not appear interesting. It would just look like a water pouring out of a nozzle that is in oscillatory motion.
Ronald
.
As Ronald has said this is simple a strobe type trick which results from the frame rate of the camera.
The sound wave in this trick is applied to the water by having the pipe connected to a speaker which is driven by a signal generator. Interestingly, if you change the frequency you can "pause" and even "reverse" the flow even though in reality and to the observer watching directly, the flow is constant.
https://www.youtube.com/watch?v=mODqQvlrgIQ
The same effect can be seen in videos of helicopters where the frame rate of the camera matches the rotation speed of the blades making it look like they arent turning
https://www.youtube.com/watch?v=2IghwseoISc
- Badges
- Science topic
- Similar topics
- Engineering
- Thermal Engineering
- Thermofluid
- Fluid Mechanics
- Fluid Dynamics