Spin up and down of vortices Rotating water in a container

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When the blades are at the center of the base

When the blades are distributed around the perimeter

When the blades are placed in the center of the base, the water starts rotating far more quickly.

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Experimental conditions

Speed: 45 rpm
Photographs were taken ten seconds after the start of rotation.

Photographic conditions

f=50mm, F3.5, 1/15 second, ASA64
Lighting done with a slide projector. The bottom half of the water tank was red, the top half blue.

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