2001 – Billowing Shower Curtains

Have you ever wondered why shower curtains move towards you when you take a shower? In 2001, David Schmidt found the answer and was awarded the Ig Noble prize for physics.

(This article was originally published at Scienceray.com on 31 December 2010.)

Shower by Tanakawho

Shower by Tanakawho

David Schmidt, like millions of other people, wondered why shower curtains billow inwards. Unlike those millions of other people, however, Schmidt had access to sophisticated computer modelling software. His research won him the 2001 Ig Noble prize for physics.

There were already two different theories to explain the phenomenon. The Bernoulli principle stated that as the water from the shower head accelerates, the pressure drops on the inside of the curtain leading to a lift effect similar to that experienced by an aircraft’s wing. The buoyancy theory, on the other hand, explained the billowing as the rushing in of cold air as the hot air inside the curtains rises.

Schmidt’s experiment, however, showed a different cause. His computer model showed that the water droplets decelerate, due to aerodynamic drag, rather than accelerate. Their energy is transferred to the air inside the curtain which forms a vortex similar to that of a hurricane. The pressure in the centre of the vortex is lower than that of the air outside, and so the curtain is pulled inwards.

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