A pair of Oxford University scientists at the American Physical Society’s Division of Fluid Dynamics conference solved an old ketchup bottle secret. Has it ever happened to you that, at the end of the bottle, trying to pour the latter contents splashing everywhere uncontrolled? Now we know why!
This is to be found in a complex fluid dynamics system, which ultimately boils down to how resistance and force affect how the sauce flows out of the bottle. Indeed, when we squeeze the full container, the air at the top compresses, pushing the liquid out in front of it (this is also science, like the one behind the perfect shape of urinals).
While this is happening, the downward force is resisted by the resistance of the ketchup against the walls of the bottle. However, when the sauce is running low, this subtle balance is disrupted by the lesser resistance of the sauce: with less resistance, the air in the package is able to unleash its full potential like a springcausing the remaining ketchup to suddenly eject.
“As the liquid flows out, the viscosity resistance decreases because there is less and less liquid to push. At the same time, liquid outflow creates more space for air to expand in the pipe, which decreases the driving force over time‘said Professor Chris MacMinn, an author of the study in the Department of Engineering Sciences at the University of Oxford.
Using mathematical models and a series of experiments, scientists have proved that squeeze the container slowly and gently it will significantly reduce the chances of runaway stains. Not only that: the researchers suggest that manufacturers should make bottle caps with wider nozzles to reduce the likelihood of the substance spreading everywhere.
By the way, did you know that a sauce was created with tomatoes grown on Mars?