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Blowing Through a Gap

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What kind of experiment is this?

Experimental procedure and explanation:

  • Two cylinders are placed beside each other with a narrow gap between them, and air is blown through the gap. When the position from which air is blown is shifted slightly, only the flame of a candle on one side is blown out.
  • This experiment uses the “Coanda effect,” i.e., a flow bends along a round object when a jet is applied to it.
  • As shown in the figure on the right, when the position from which air is blown is shifted slightly to the left, the flow begins to follow the left cylinder, advances along the left cylinder, bends left, and flows outward. As a result, only the flame of the candle on the left is blown out.
  • When a jet is injected through the gap, the flow easily bends to the right or the left depending on the size of the gap.
[Keywords] Coanda effect
[Related items] Blowing Out a Candle Behind a CylinderCandle Behind a Flat Plate

“The Wonders of Flow,” Japan Society of Mechanical Engineering, Kodansha Blue Backs, pp.128-133

Last Update:1.21.2015