Why Does The Shower Curtain Move Toward The Water? | Showering Enthusiast

Scientif American:

David Schmidt, an assistant professor at the University of Massachusetts Amherst, provides the following explanation:
Maybe it happened to you this morning: you entered the shower and the curtain moved in to engulf you. I have recently discovered a new explanation for this common phenomenon, thanks to modern fluid-simulation technology.

As an assistant professor in the mechanical and industrial engineering department, I research ways to accurately simulate sprays. Typically we use these spray simulations to help design better diesel and aircraft engines. The same analysis, however, is equally applicable to a bathroom shower. The shower is, after all, just a large spray.

Until now, explanations for the shower curtain’s movements were theoretical. It was one person’s opinion versus another’s, with most ideas drawing on the Bernoulli effect or on so-called buoyancy effects. The Bernoulli effect is the principle that explains how an airplane’s wings produce lift. It says that as a fluid accelerates, the pressure drops. But the Bernoulli effect is based on a balance between pressure forces and acceleration, and does not allow for the presence of droplets. Nor, according to my calculations, is it responsible for the curtain deflection.