Is this due to the Coandă Effect? (Part 1)

Let's take a look!

What type of experiment is this?

Experimental procedure and explanation:

• Some have suggested that the reason the water dome grows larger may be due to the Coandă effect. However, is this explanation valid?
• The Coandă effect refers to the tendency of a fluid jet to be attracted to a nearby curved surface and to follow its contour. (A jet is a stream of fluid emitted from a nozzle or pipe—in this case, the flow from a water faucet qualifies as a jet.)
• In this experiment, there are two possible ways the Coandă effect could be involved. One of these is at the rounded edge of the plastic bottle cap.
• When the cap’s rim is rounded, the Coandă effect can cause the water to curve along the cap and flow down the sides of the bottle, disrupting the formation of the dome. In such cases, the dome does not form properly, and the experiment may fail. In other words, the Coandă effect can be counterproductive.
• Therefore, a cap with flat edges is more suitable for this experiment.
• This video was produced with the support of the JSPS Grant-in-Aid for Scientific Research (18K03956).

[Attention]	Water is used throughout these experiments, but it’s important to remember that water is a valuable resource. To minimize waste, consider reusing the water after each experiment—for bathing, cleaning, watering plants, and other practical purposes.
[Keywords]	Coandă effect
[Related items]	Why does the Water Dome Grow Larger? , Is this due to the Coandă Effect? (Part 2)
[References]	Ryozo Ishiwata and Mitsumasa Nemoto, “The Wonder of Flow,” Kodansha Bluebacks, pp. 128–133. Ryozo Ishiwata, “Illustrated Fluid Dynamics Trivia,” Natsume Publishing, pp. 214–215.

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