River depth and speed of flow 1

Let's take a look!

What type of experiment is this?

Experimental procedure and explanation:

• How does the speed of a river change with depth? Let’s confirm with the aid of experiments.
• We created a shallow area in a part of the straight section of the river flow experimental device. The gray part in the video is the shallow section (approximately 2 mm deep), and the black part is the deep section (approximately 12 mm deep).
• We can float a small piece of paper in the current to detect the slowing down of water flow in shallow water because viscous friction acts between the riverbed and water, breaking the flow, which affects the shallow water area the most. In contrast, the effect of viscous friction is weaker in the deep section except near the river bed, resulting in less deceleration of the flow.
• The phenomenon of slower flow in the shallow water area due to viscous friction occurs when the water is shallow. If the water depth is sufficient, then the deceleration is not very significant.

[Keywords]	Relationship between water depth and speed, viscous friction
[Related items]	Water and syrup 2、River depth and speed of flow 2
[Reference]	“The Wonders of Flow,” Japan Society of Mechanical Engineering, Kodansha Blue Backs, p. 16–21.

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