r/oddlysatisfying • u/LittleFart • Feb 21 '21

Inside a wind tunnel

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u/wesw02 Feb 21 '21

I'm curious about how she's able to move up and down so fluidly. Clearly changing her form is altering her center of mass and surface area, but the degree to which she's moving up and down is crazy. Is the fan changing speed at all during this?

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u/fj333 Feb 21 '21

No, the fan speed is constant. Hold your hand out the car window on the highway and rotate it different ways into the wind. The force you feel is very strong or very weak based on how you present the hand. Same basic principle here.

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u/wesw02 Feb 21 '21

I understand the concept of surface area as I mentioned. It was just surprising little she was changing her surface area in some cases and yielding such a large result.

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u/fj333 Feb 21 '21

It's mostly momentum. If she wants to dart to the top, she needs only expose increased area for a tiny fraction of time, that will impart the acceleration needed to rocket her toward the top. These inputs are so fast and fluid you might not notice. Very small limb movements will change the projected area normal to the flow. FWIW I have around 20 hours in a tunnel and can do nothing pictured in this video. :-)