Why do shower curtains encroach your showering space ?
You are all set to kick start your day with a shower; You open the faucet and notice that immediately the shower curtain starts to bulge in to your showering space (irrespective of whether its hot or cold water).
What on earth is happening here?
Shower- Curtain effect
In 2001, Prof.David Schmidt from the University of Massachusetts won his way to the Ig Nobel prize when he found out that the reason why the curtain bends is Vortices!
Let’s run through the logical theories to explain this effect:
Buoyancy effect :
Hot air raises and cooler air moves down, and this causes the shower deflection. True only for hot air, but doesn’t explain why the curtain deflects even for cold water.
Pressure in a fluid decreases as its velocity is increased. The fast moving water molecules in the shower causes the pressure inside the shower lower than outside.
Since this pressure is lower than outside, this pressure differential independent of temperature would cause the curtain movement..
When Prof.Schmidt ran his simulation, he found out that the spray of water droplets from the shower formed a vortex with its axis normal to the plane of the curtain.
And the pressure at the center of this vortex was lower than those predicted by either effect separately or combined:
Velocity vectors of air molecules in the shower. (Notice the circulation of air)
Result : The deflection of the curtain
And now we understand that the major contributor that causes the deflection of the curtain is the vortex. But we are still in the dark when it comes to a theory to explain the Shower-curtain effect (A fun research project if anyone is interested).
The next time you step in to take a shower and furious about the damn curtain encroaching all your showering space, just know that a IgNobel was awarded and many research articles published in trying to answer your frustration.*
Physics is life, Have a good one!
* or get a shower weight / a heavier curtain that would prevents this from happening.