This video is an excerpt from "Hidden By Time: Seeing the Physical World with High-Speed Cameras," an educational DVD from Physics Curriculum & Instruction.
www.PhysicsCurriculum.com/hidd...
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Camera Imaging: 500 frames/sec
Playback: 30 frames/sec
Slow Motion Factor: 17
Using smoke as a tracer to make the flow of air visible, the blades of a household fan are seen to produce spiraling vortices in the forced air flow. Rotating at 590 rpm, the fan's three blades are perceived as a blurred disc to the unaided eye.
With the high-speed camera, the rapidly rotating blades become defined with vortices observed to be produced at the tip of each blade. the turbulent vortices swirl rapidly, initially undergoing one revolution in just 0.03 seconds.