Is this due to the Coandă Effect? (Part 2)

Let's take a look!

What type of experiment is this?

Experimental procedure and explanation:

• In this experiment, there are two possible ways the Coandă effect could be involved. The second concerns how easily the water film breaks.
• To investigate this, I inserted both a round stick and a square stick into the water film and compared how easily the film broke in each case. With a round stick, the Coandă effect can potentially cause the water flow to curve around to the back of the stick. However, when the stick is about as thick as a finger, the flow does not curve around the back of either stick—regardless of shape—and the water film breaks in both cases. In both scenarios, the water dome grows larger after the film breaks.
• When a thin, round stick—such as a bamboo skewer—is inserted into the water film, the Coandă effect causes the water to flow around to the back of the stick. As a result, the water film does not break, and there is little change in the size of the water dome. In other words, the Coandă effect no longer contributes to an increase in dome size and can, in this context, actually suppress its growth.
• In line with the findings from the previous section, “Is this due to the Coandă Effect? (Part 1),” it appears that the Coandă effect is not the reason the water dome increases in size. In fact, it has been shown that in some cases, it can inhibit the dome from growing larger.
• 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 1), Circle and Square 3 (Flow Field)
[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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