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I am using this flat bottle:

I fixed a motor at the centre of one of the flat sides and attached an impeller. I thought this will create some kind of whirlpool effect but as you can guess, since the motor is horizontal, the water also rotated about a horizontal axis. But it did not create any much effects. I turned up the power but I was afraid my motor could not get any faster.

My question is: do you think if I install a more powerful and faster motor, it will eventually create a mini vortex/whirlpool? If you saw the picture, the width of bottle is only around 2cm so its not very taxing I think?

What I am originally trying to do is to create some kind of continuous cool effect in the bottle. I initially planned to do something like this lava lamp by using pump to continuously circulate water in oil instead of the alka seltzer but it ended up mixing the oil and water into a cloudy solution. Another option was to create bubbles but I don't like that as its very generic.

So is it possible to create horizontal whirlpool/vortex? Or is there any other cool effects you can suggest I can make?

enter image description here

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  • $\begingroup$ Can you post a video and images of what you did, and describe in more detail what you hope to achieve? $\endgroup$
    – mart
    Sep 10, 2021 at 8:40
  • $\begingroup$ I have edited the question now with actual photo. $\endgroup$ Sep 10, 2021 at 9:13

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This is a very short answer on a very wide and interesting subject.

Try different impellers, (look for vortex impellers on google) e.g.:

enter image description here

or

enter image description here

Different designs would require different power to achieve a similar effect depending on viscosity and density of the liquid.

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  • $\begingroup$ So a horizontal vortex can be created? Is it a possibility if I use a suitable impeller? $\endgroup$ Sep 10, 2021 at 6:34
  • $\begingroup$ I am not sure what would you qualify as vortex (i.e. separation from the walls). It should be possible in a larger setup. In the confines of those plastic bottles, I am a bit skeptical to be honest, although I don't have much experience in agitators and those types of processes. $\endgroup$
    – NMech
    Sep 10, 2021 at 6:38
  • $\begingroup$ Horizontal, vertical only matter because of gravity so in theory if you can overpower gravity significantly, it won't matter. The issue with your bottle is getting the flow you seek. You would have to circulate air all the way from the top to your impeller for the visual effect you want. More air, less liquid might help, or putting the water-oil divide closer to the motor maybe with one of these impellera $\endgroup$
    – Abel
    Jun 13 at 11:37
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I try to translate what you want to achieve into engineering terminology:

  • you want to create a circular flow across the whole volume
  • you want to entrain oil bubbles into this flow
  • you don't want to shear these bubbles into very small sizes, they should remain individually visible - in effect, you want to create the opposite of a fine emulsion

A process engineer designing a system to create a fine emulsion would choose a fast spinning impeller for high shear forces. So do the opposite:

  • lower motor power until the droplet size increases to what you find visually appealing
  • if there's no flow across the whole volume, increase impeller size - you may need to increase motor power with it, but generally large impellers are more efficient at creating large bulk flow - that may be up for experimenting
  • It is entirely possible that at fluid speeds you like visually, the oil will form a stable layer on the water

Normally a vortex in a mixed vessel looks like in a kitchen mixer - upward at the walls of the vessel, inward at the surface of the fluid, downward at the center of the vortex, outward where the actuall mixer , the spinning part, is. Your vessel is so flat and the axis is horizontal so you won't achieve this three dimensional flow. Because your vessel is so flat it will likely be a more 2D flow.

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  • $\begingroup$ Ok so you are saying creating vortex is not possible for my setup sadly. $\endgroup$ Sep 10, 2021 at 9:50
  • $\begingroup$ But you did give me another idea! I will fill bottle with water till the height of motor and then the rest half with oil. Then using larger impeller with lower speed, I should be able to keep the bubbles without mixing into emulsion. By filling water and oil to half the height, oil will always be in contact with impeller too. Neat! $\endgroup$ Sep 10, 2021 at 9:55
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The basics of the vortex are to generate varying velocity along the axis it rotates about and creating the drag effect, which involves the pressure differential. Due to the shallow depth of the bottle, I doubt the environment and geometry of the bottle meet the necessities for vorticity to occur, so, it seems unlikely.

Please read the linked articles that might provide useful clues.

https://en.wikipedia.org/wiki/Vortex https://journals.biologists.com/jeb/article/214/13/2283/10347/Characteristics-of-vortex-formation-and-thrust

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What you are asking for, is called cavitation bubbles. Typically, this is a harmful phenomenon in the field of ship propeller screws. It is accompanied by vibration and noise, so likely you will not wish this will last long in your room. Visible cavitation will require more power and rotation speed than that motor gives, or smaller propeller. There are many articles and videos in the net about screw (propeller) cavitation.

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