Splattered Legs, Begone
Splattered Legs, Begone
Urinals are notorious for splash-back, but a team of engineers has designed the answer: a urinal that actually catches all the pee.
The men’s room is so often an assault on the senses. The urochrome stained tiles, the nostril-narrowing wafts of ammonia, the tacky resistance nipping at the soles—these are all the sad result of flights of urine that have strayed from their intended path.
“Sad” because nearly 200 years of urinal design and evolution have done nothing to curb the offending splashes. In fact, they seem designed more to encourage splatter than mitigate it. “The current urinals—I don’t quite understand it, maybe it’s the inertia of the design, or concerns behind the cost—but the old designs are like a bowl,” said Zhao Pan, a professor of mechatronics and mechanical engineering at the University of Waterloo, where he runs the Pan-Lab.
Now, at last, Pan and his team of researchers at Waterloo have designed a urinal that does what it’s supposed to: catch all the pee.
Before golden streams became a subject of research for Pan, he studied fluid behavior of many colors at Utah State University’s Splash Lab (which has since moved to the King Abdullah University of Science and Technology).
“Droplets or jets impinging on a surface, causing splash—this is always active research in our field, in fluid mechanics,” he said. The idea of creating a better urinal first occurred to him when he noticed (and subsequently teased) a fellow student at the lab who always returned from the bathroom with dampened khakis.
Testing high flow urine streams on four urinals (from left) Duchamp’s “La Fontaine,”
a contemporary commercial model, the Cornucopia, and the Nautilus. Video: Zhao Pan
Pan wondered if he could help his fellow students, and men the world over, avoid such sartorial defilement.
He soon examined the properties of dessert moss, which, thanks to their tiny water-wrangling hairs, reduce splash when drops or streams of water hit them. Ultimately though, he wanted to “just design a good urinal so that we don’t need any accessories like the urinal pad,” Pan said.
To do that, he took a good look at what he calls the “impinging stream angle.” Fire a jet of water at a perpendicular surface and a lot of it ends up coming back at you. But if you make the angle of the stream to surface impact shallow enough, splashing is reduced to near nil, as anyone who’s washed dishes by hand can attest.
“If we could somehow find this magic angle,” said Pan, “then we could design the urinal so that—no matter how you do the business—at any moment during the course of urination, the impinging angle is always smaller or equal to that critical or magical angle.”
This was a more difficult task than just sending a stream at a surface and tilting it until there’s no splash. After all, emanations from male pee-ers change dramatically as they slow to a stop. “It’s a family of parabola, depending on the starting or the end of the course, depending on the age, and depending on the bladder pressure, and so on,” Pan said. “So, at the beginning, the parabola is pretty flat, and at the end, the parabola drops really fast.”
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In the end, they found their angle: 30 degrees. When that impinging angle is larger, the fluid begins to spray. Smaller can be better, but not by much. “The margin of the benefits for going down, in terms of the reducing the splash, is very small,” Pan said. And reducing the angle below thirty would make for impractical designs.
Pan and his team used his magic angle to create two urinals. Two, because ADA accessibility standards dictate that every bathroom with more than one urinal needs to have at least one at a lower height. The researchers used a “pseudo-urethra nozzle” to compare the performance of their designs against the most common urinals in the U.S. and Canada, as well as the one used in Duchamp’s sculpture, “La Fontaine.”
One came out the clear winner: the Nauti-loo. The first author of the paper discussing this innovation, Kaveeshan Thurairajah, came up with the name. “Loo,” of course, is British English for bathroom, but also echoes the “loo” in Waterloo. “Nauti” refers to the off-color nature of the research as well as the math behind the design.
“We have to solve differential equations, and the solution that governs our urinal is the same as the equation that governs the Nautilus seashell,” Pan explained. “So, there are lots of layers behind this thing.”
PNAS Nexus, the journal that published their paper this April, “Splash-free urinals for global sustainability and accessibility: Design through physics and differential equations,” was less appreciative of the wordplay and forced them to change the name of the urinal to Nautilus (at least for the purposes of publication).
From left are 3D models of four urinals: Duchamp’s “La Fontaine,” a contemporary commercial model, the Cornucopia, and the Nautilus. Below these are maps of impinging angles on urinals and histograms showing percent of the area at various impinging angles. Image: Thurairajah et al.
The Nautilus/Nauti-loo design is essentially two long slabs that form a narrow angle, the vertex of which is against the wall. Just above the floor, the sides curl up, in that Nautilus-like logarithmic spiral, so that a stream of fluid will hit the sides of the urinal at less than 30 degrees, even as it slows to a stop at micturition’s end. Thanks to its height, the angle of impingement is less than 30 degrees, no matter how tall the urinator.
There is a place on the urinal where a stream hitting it will not have a less-than-30-degree angle: the vertex. So a little aim on the man’s part in the bathroom is still in order.
“From the mathematics perspective, that’s a line—it’s impossible to hit because a line has no area,” Pan said. “However, now we are talking about physics and engineering, right? So the user should avoid shooting jets to that line, otherwise they will splash.”
Another Bathroom Innovation: Self-Lifting Mechanism Could Settle Toilet Seat Wars
There is no such line on the team's Cornuco-pee-a, or Cornucopia for publication, which has a curved back to keep the angle of impingement acute enough. It also has a smaller opening, so, in terms of reducing splash, it makes for a slightly superior urinal. However, its more closed design means it would be harder to manufacture and harder to clean. And its opening is positioned higher, so it’s not accessible to children and people in wheelchairs.
The Nauti-loo is already in demand. Target has reached out to Pan, as has a Japanese toilet manufacturer and an American construction company hoping to put the urinals in upscale homes. The patent must first go through before anyone builds one for actual use.
But there is a side-effect of the research that Pan finds more inspiring than the prospect of cleaner bathrooms: fan mail from children and high school students. “One impact we made using this humble research is that a lot of kids find the physics, and the math, and the art and engineering, interesting. And they want to know more,” he added.
Michael Abrams is a technology writer in Westfield, N.J.
“Sad” because nearly 200 years of urinal design and evolution have done nothing to curb the offending splashes. In fact, they seem designed more to encourage splatter than mitigate it. “The current urinals—I don’t quite understand it, maybe it’s the inertia of the design, or concerns behind the cost—but the old designs are like a bowl,” said Zhao Pan, a professor of mechatronics and mechanical engineering at the University of Waterloo, where he runs the Pan-Lab.
Now, at last, Pan and his team of researchers at Waterloo have designed a urinal that does what it’s supposed to: catch all the pee.
Before golden streams became a subject of research for Pan, he studied fluid behavior of many colors at Utah State University’s Splash Lab (which has since moved to the King Abdullah University of Science and Technology).
“Droplets or jets impinging on a surface, causing splash—this is always active research in our field, in fluid mechanics,” he said. The idea of creating a better urinal first occurred to him when he noticed (and subsequently teased) a fellow student at the lab who always returned from the bathroom with dampened khakis.
Testing high flow urine streams on four urinals (from left) Duchamp’s “La Fontaine,”
a contemporary commercial model, the Cornucopia, and the Nautilus. Video: Zhao Pan
He soon examined the properties of dessert moss, which, thanks to their tiny water-wrangling hairs, reduce splash when drops or streams of water hit them. Ultimately though, he wanted to “just design a good urinal so that we don’t need any accessories like the urinal pad,” Pan said.
To do that, he took a good look at what he calls the “impinging stream angle.” Fire a jet of water at a perpendicular surface and a lot of it ends up coming back at you. But if you make the angle of the stream to surface impact shallow enough, splashing is reduced to near nil, as anyone who’s washed dishes by hand can attest.
“If we could somehow find this magic angle,” said Pan, “then we could design the urinal so that—no matter how you do the business—at any moment during the course of urination, the impinging angle is always smaller or equal to that critical or magical angle.”
This was a more difficult task than just sending a stream at a surface and tilting it until there’s no splash. After all, emanations from male pee-ers change dramatically as they slow to a stop. “It’s a family of parabola, depending on the starting or the end of the course, depending on the age, and depending on the bladder pressure, and so on,” Pan said. “So, at the beginning, the parabola is pretty flat, and at the end, the parabola drops really fast.”
Discover the Benefits of ASME Membership
In the end, they found their angle: 30 degrees. When that impinging angle is larger, the fluid begins to spray. Smaller can be better, but not by much. “The margin of the benefits for going down, in terms of the reducing the splash, is very small,” Pan said. And reducing the angle below thirty would make for impractical designs.
Pan and his team used his magic angle to create two urinals. Two, because ADA accessibility standards dictate that every bathroom with more than one urinal needs to have at least one at a lower height. The researchers used a “pseudo-urethra nozzle” to compare the performance of their designs against the most common urinals in the U.S. and Canada, as well as the one used in Duchamp’s sculpture, “La Fontaine.”
One came out the clear winner: the Nauti-loo. The first author of the paper discussing this innovation, Kaveeshan Thurairajah, came up with the name. “Loo,” of course, is British English for bathroom, but also echoes the “loo” in Waterloo. “Nauti” refers to the off-color nature of the research as well as the math behind the design.
“We have to solve differential equations, and the solution that governs our urinal is the same as the equation that governs the Nautilus seashell,” Pan explained. “So, there are lots of layers behind this thing.”
PNAS Nexus, the journal that published their paper this April, “Splash-free urinals for global sustainability and accessibility: Design through physics and differential equations,” was less appreciative of the wordplay and forced them to change the name of the urinal to Nautilus (at least for the purposes of publication).
From left are 3D models of four urinals: Duchamp’s “La Fontaine,” a contemporary commercial model, the Cornucopia, and the Nautilus. Below these are maps of impinging angles on urinals and histograms showing percent of the area at various impinging angles. Image: Thurairajah et al.
There is a place on the urinal where a stream hitting it will not have a less-than-30-degree angle: the vertex. So a little aim on the man’s part in the bathroom is still in order.
“From the mathematics perspective, that’s a line—it’s impossible to hit because a line has no area,” Pan said. “However, now we are talking about physics and engineering, right? So the user should avoid shooting jets to that line, otherwise they will splash.”
Another Bathroom Innovation: Self-Lifting Mechanism Could Settle Toilet Seat Wars
There is no such line on the team's Cornuco-pee-a, or Cornucopia for publication, which has a curved back to keep the angle of impingement acute enough. It also has a smaller opening, so, in terms of reducing splash, it makes for a slightly superior urinal. However, its more closed design means it would be harder to manufacture and harder to clean. And its opening is positioned higher, so it’s not accessible to children and people in wheelchairs.
The Nauti-loo is already in demand. Target has reached out to Pan, as has a Japanese toilet manufacturer and an American construction company hoping to put the urinals in upscale homes. The patent must first go through before anyone builds one for actual use.
But there is a side-effect of the research that Pan finds more inspiring than the prospect of cleaner bathrooms: fan mail from children and high school students. “One impact we made using this humble research is that a lot of kids find the physics, and the math, and the art and engineering, interesting. And they want to know more,” he added.
Michael Abrams is a technology writer in Westfield, N.J.
