## Why does the shower curtain move towards the water?

The worst part about taking a shower is getting attacked by the wet shower curtain. Luckily, David Schmidt discovered a logic explanation for why this happens so often and you are about to hear it.

To do the calculation, I drafted a model of a typical shower and divided the shower area into 50,000 minuscule cells. The tub, the showerhead, the curtain rod and the room outside of the shower were all included. I ran the modified Fluent software for two weeks on my home computer in the evening and on weekends (when my wife wasn’t using the computer). The simulation revealed 30 seconds of actual shower time.

When the simulation was complete, it showed that the spray drove a vortex. The center of this vortex¿much like the center of a cyclone¿is a low-pressure region. This low-pressure region is what pulls the shower curtain in. The vortex rotates around an axis that is perpendicular to the shower curtain. It is a bit like a sideways dust devil. But unlike a dust devil, this vortex doesn’t die out because it is driven continuously by the shower.

For an in depth explanation, click here.

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## 2 Comments.

1. I always just assumed it was the hot water heating the air inside the curtain, lowering the pressure, and thus sucking the curtain in. It’s certainly a much simpler explanation.

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• You are most correct in your assumption, that is the real reason for why the shower curtain gets sucked in. Although, it is not impossible that the warm air that rises takes the shape of a vortex – it might be that which he saw in his calculations.

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