Bubbles in a vortex

Let's take a look!

What type of experiment is this?

Experimental procedure and explanation:

• We will conduct an experiment with vortices using a device called a stirrer. A stirrer is a device that stirs a liquid by rotating a magnet (rotor) in the liquid through a rotating magnetic field.
• We start the stirrer to rotate the water in the tank and create a vortex.
• Next, when bubbling bath salts are placed in it, the generated bubbles will accumulate in the center of the vortex.
• In a vortex, the rotation causes the apparent force from the water, the Centrifugal force (centrifugal effect), and this causes a high pressure on the outside and low pressure at its center. This difference in pressure causes smaller density bubbles to gather at the center of the vortex.
• In the previously published " Ring of Air  ," the pressure drops at the center of the rotation of the vortex ring of air and bubbles gather. Substances with a small density (in this case, air) gather inward due to the force of the pressure difference between the inside and outside (or more precisely, due to the pressure gradient).
• In the previously " Centrifuge ", the densely packed material gathered on the outside. This is because the apparent centrifugal force acting on the material is greater than the force due to the pressure difference.
• This experimental video was produced with the support of JSPS Grant-in-Aid for Scientific Research 18K03956.

[Keywords]	Vortex
[Related items]	Ring of Air, Centrifuge, Centrifugal force
[Reference]	Ryozo Ishiwata, "The Wonder of Flow," Kodansha Blue Backs, p. 52-61.

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