What’s the finest design for a splash-free urinal? Now physics has a solution
Scientists on the College of Waterloo have recognized the optimum design for a splash-free urinal: a tall, skinny porcelain construction with curves harking back to a nautilus shell, playfully named “Nauti-loo.” That is excellent news for males who’re uninterested in urine splatters on their pants and sneakers, and for poor ladies who should usually clear up all of the splatters. Bonus: It is a fairly aesthetically pleasing design that provides this workhorse of a public restroom a contact of sophistication.
“An thought is born precisely the place you suppose it’s.” Waterloo Zhao Pan mentioned New Scientist. “I feel most of us have been a bit careless at our submit and regarded down to seek out we have been carrying noticed pants. No one likes to pee all over the place, so why not simply create a urinal the place splashing could be very unlikely?” His graduate scholar, Kavishan Thurairaja, offered the outcomes of this research in the course of the American Bodily Society (APS) final week assembly on hydrodynamics in Indianapolis.
This isn’t the primary time that scientists have tried to resolve this downside. Pan is a former graduate scholar of Tad Truscott, a mechanical engineer who based the so-calledSplash Lab” on the College of Utah. In 2013, the Splash Lab (then at Brigham Younger College) supplied some useful tips about tips on how to maintain males from splattering their khaki pants once they go to the lavatory. “The perfect factor to do is to take a seat on the technician’s bathroom, as a result of urine has to journey a shorter distance on its approach to the bowl,” I mentioned wrote earlier in Gizmodo. “If you happen to select the basic standing method, scientists advise standing as near the urinal as potential and making an attempt to direct the stream at a downward angle in the direction of the again of the urinal.”
For these missing optimum spatter management methods, one other of Truscott’s graduate college students, Randy Hurd, offered optimum design for splash-free urinal insertion 2015 12 months APS Hydrodynamics Assembly. There are three principal sorts of inserts. One makes use of an absorbent material to maintain splashes to a minimal; one other makes use of a honeycomb construction – a raised layer (supported by small pillars) with holes – in order that drops of urine go via however splashes don’t escape; and a 3rd kind with many pillars. Nonetheless, the absorbent tissues can not take in the liquid quick sufficient and are quickly saturated, whereas the honeycomb and columnar constructions don’t forestall the gradual formation of urine puddles.
The design of the Hurd and Truscott insert was impressed by a sort of superabsorbent moss (Syntrichia caninervis), which thrives in very dry climates and is therefore very good at collecting and storing as much water as possible. And they discovered that a man-made material called “VantaBlack” mimicked the absorbent properties of moss. They copied the structure of this material to insert into a urinal and found that it successfully blocked the exit of urine droplets – effectively acting as a “black hole in the urinal”.
The ladies weren’t left out of this scientific (ahem) writing competition either. Women also suffer from leakage of urine, especially when required to urinate in a cup for medical examinations. In 2018, Splash Lab conducted a series of experiments on a model of an anatomically correct female urethra. (They used a soft polymer to model the labia.) The the results are inspiring (proprietary) “Orchid” design, a funnel-shaped attachment for urine cups that reduce spillage. The research could lead to devices that allow women to urinate while standing up, which would be a boon for women in the military and women in academics working in the field.
According to Pan, the key to optimal splash-free urinal design is the angle at which the stream of urine hits the porcelain surface; get a small enough angle and there won’t be any splash. Instead, you get a smooth flow over the surface, preventing the droplets from flying out. (And yes, there is a critical threshold at which the stream of urine switches from a spray to a smooth one, because phase transitions are everywhere—even in our public toilets.) It turns out that dogs have already determined the optimal angle by lifting their legs to urinate, and when Mr. and others. after simulating this on a computer, they determined the optimal angle for humans to be 30 degrees.
Peng and his team also conducted a series of experiments with dyed liquids sprayed at varying speeds into a series of mock urinal designs (see top photo) made of dense foam coated with epoxy resin, including a standard commercial mold and a urinal similar to this one. , which Marcel Duchamp used in his famous (and controversial) 1917 art installation “Fountain.” All produced varying degrees of splashes, which the scientists wiped up with paper towels. They weighed the wet towels and compared them to the weight of the dry paper towels to quantify the amount of splashes. The heavier the wet towels, the bigger the splash.
The next step was to figure out a design that would offer the optimal angle of urine flow for men across a wide range of heights. Instead of the usual shallow box in the shape of a rectangle, they landed on the curved structure of the nautilus shell. They repeated the urine jet simulation experiments with prototypes, and that’s it! They did not notice a drop that splashed back. In comparison, other urinal designs produced 50 times more spray. There was one circular design with a triangle shaped opening that worked even better than the Nauti-loo in experiments, but Pan and others. rejected it because it wouldn’t work over a wide range of altitudes.
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