Engineering researchers at the University of Waterloo in Ontario, Canada, followed their curiosity and called on nature for inspiration for a new urinal design that has attracted international attention by solving the messy problem of splash-back.
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The long, sleek design all but eliminates splatter on floors and shoes by ensuring that the angle at which a urine stream hits the urinal wall doesn’t exceed roughly 30°, a measurement determined via physical experiments and computer modelling.
‘We found that when a liquid jet or droplet train impacts a rigid surface below a certain critical impinging angle, almost no splatter is generated,’ the researchers wrote. ‘Thus, a surface designed to always intersect the urine stream equal to or smaller than the critical angle prevents splash-back.’
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Zhao Pan, a professor of mechanical and mechatronics engineering at Waterloo who led the project over the course of several years, said that much of the work was carried out by undergraduate students in his lab. ‘This urinal design project is the best teaching tool I can think of, as it is a daily-life problem that covers numerous topics, including fluid mechanics, sustainability, differential equations, manufacturing and prototyping, art, industrial design, human factors, bio-mechanics and testing,’ he said.
‘What makes research rewarding and drives discovery is finding a nut to crack, one which has slipped the eyes of those before us,’ said undergraduate Kaveeshan Thurairajah, who worked on the study for about two years and is now in his final year of the mechanical engineering programme.
Inspiration for the new urinal design came from the way in which dogs lift their hind legs to urinate against trees, a behaviour that instinctively minimises the impact angle, and the curving structure of nautilus shells. The result is a ‘splash-free urinal’ with a special narrow opening and a curved inner surface designed to prevent droplets from flying out, regardless of how tall the user is or where he aims.
‘Our new urinal designs will keep bathrooms cleaner and reduce the labour, water and chemicals required for periodic cleaning to promote more sustainable bathroom maintenance,’ the researchers wrote.
The project involved tests with jets of coloured fluids at different speeds and heights with five urinals, including a widely used North American urinal, a replica of a famous sculpture by artist Marcel Duchamp and three original designs (pictured above). Their effectiveness was measured by wiping the splattered mess with a paper towel after each experiment and weighing it to determine the mass of liquid picked up.
‘The idea for this project truly originated – well, exactly where you think it did,’ said Pan, director of the Pan-Lab for fluid physics. ‘When you study fluid behaviour all day, you can’t help but wonder about these everyday scenarios. The fun part is that we are solving a real-world problem affecting 50 per cent of humans.’
