Q: Why, oh why does the shower curtin blow in when I’m in the shower?

A: A vortex.

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.