Norman Bates framed by shower curtain?

To attack the shower curtain problem, I used software designed by Fluent Inc., a New Hampshire-based software company that contracted my consulting firm, Convergent Thinking LLC, to add advanced spray models to their software. The simulation took advantage of the fruits of this project. I was able to include the effects of the drops breaking up. Even more important, the new spray models captured the distortion of the droplets, which tends to increase their aerodynamic drag. This drag is the force between the air and the water that imparts motion to the air and slows the droplets.

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.

Why does the shower curtain move towards the water? [Scientific American]