What’s the best design for splash-free urinal? Physics now has the answer - Ars Technica

Scientists at the University of Waterloo have determined the optimal design for a splash-free urinal: a tall, slender porcelain structure with curves reminiscent of a nautilus shell, playfully dubbed the "Nauti-loo." That's good news for men tired of having urine splash onto their pants and shoes—and for the poor souls who have to regularly clean up all the splatter.

In 2013, the Splash Lab (then at Brigham Young University) offered a few handy tips on how men could avoid staining their khaki pants with urine splashback while relieving themselves in restrooms.

"If you opt for the classic standing technique, the scientists advised standing as close to the urinal as possible, and trying to direct the stream at a downward angle toward the back of the urinal.".

For those who lack optimal anti-splash technique, another of Truscott's graduate students, Randy Hurd, presented an optimal design for a splash-free urinal insert at the 2015 APS fluid dynamics meeting.

Hurd and Truscott's insert design drew inspiration from a type of super-absorbent moss (Syntrichia caninervis) that thrives in very dry climates and thus is very good at collecting and storing as much water as possible.

They copied that material's structure for their urinal insert and found it successfully blocked droplets of pee from escaping—effectively acting as a "urinal black hole.".

According to Pan, the key to optimal splash-free urinal design is the angle at which the pee stream strikes the porcelain surface; get a small enough angle, and there won't be any splashback.

(And yes, there is a critical threshold at which the urine stream switches from splashing to flowing smoothly, because phase transitions are everywhere—even in our public restrooms.) It turns out that dogs have already figured out the optimal angle as they lift their legs to pee, and when Pan et al.

The next step was to figure out a design that would offer that optimal urine stream angle for men across a wide range of heights.

They repeated the simulated urine stream experiments with the prototypes, et voila.