The reason why ketchup scatters from an almost empty bottle is scientifically elucidated

When trying to squeeze out ketchup from an almost empty bottle, there are many people who have experienced the ketchup suddenly scattering and staining their desks and clothes. A research team of Oxford University scientist

Callum Cuttle and others devised a theoretical model based on experiments as to why ketchup is likely to splatter from bottles that are nearly empty.

Dynamics of compressible displacement in a capillary tube
https://doi.org/10.48550/arXiv.2112.12898

New mathematical model could help avoid spattering squeezy sauce bottles
https://eng.ox.ac.uk/news/new-mathematical-model-could-help-avoid-spattering-squeezy-sauce-bottles/

Oxford scientists crack case of why ketchup splatters from near-empty bottle | Ars Technica
https://arstechnica.com/science/2022/11/the-physics-of-keeping-those-last-bits-of-ketchup-from-splattering/

'It's annoying, potentially embarrassing, and ruins clothes,' said Cuttle, who presented the findings at the American Physical Society 's Fluid Mechanics Division annual meeting in November 2022. It's possible, but what can we do about it?' 'More importantly, could understanding this phenomenon help other problems in life?'

Unlike water, ketchup is a non-Newtonian fluid whose viscosity changes according to the applied force, unlike a Newtonian fluid whose viscosity does not change due to the force ( shear stress ) that makes it slide parallel to the surface. In addition to ketchup, non-Newtonian fluids include blood, yogurt, gravy sauce, mud, etc., and ketchup has properties like 'soft solid' rather than liquid.

Mr. Cuttle conducted an experiment with Associate Professor Chris MacMinn of Oxford University to elucidate the phenomenon that the remaining ketchup scatters. The research team injected ketchup and various amounts of air into the syringe and pushed it out to see if the amount of air affected the flow rate of ketchup and whether it splattered. He also repeated experiments in which silicone oil was used instead of ketchup to control viscosity and other variables.

As a result of the experiment, it was found that a syringe filled with 1 ml or more of air causes a phenomenon of splashing when pushing out the fluid. ``This result shows that some air is needed in the syringe or bottle to generate splashes and create an unstable flow,'' Cuttle said.

According to the research team, there is a certain threshold for ketchup to splash from the mouth of the bottle, and when it is below the threshold, the air pressure and ketchup flow are balanced, so ketchup flows smoothly. He said he would come. However, when the threshold is exceeded, the air is over-compressed and the force that pushes the ketchup out increases, which reduces the viscosity of the ketchup, causing it to splash out of the mouth of the bottle like a liquid, Cuttle et al. doing.

Mr. Cuttle argues that when the ketchup runs low, it is necessary to push the bottle out as much as possible, and as a result, the ketchup is more likely to splatter. 'When the bottle approaches empty, the contents are mostly air. When you squeeze the bottle, the air inside is compressed, and the pressure is applied and the ketchup scatters outside.'

Ketchup splattering is a problem of pressure when pushing out, so you can reduce the risk of ketchup splattering by slowly squeezing the bottle to slow down the air compression speed. It is also effective to remove the ketchup cap when the bottle is empty and let the ketchup come out of the larger diameter neck. 'The valve on the cap helps prevent ketchup leaks, but from a purely ketchup splatter standpoint, it makes sense to remove the valve,' Cuttle said. There is a rigorous mathematical framework underpinning

The results of this study go beyond simply understanding ketchup splattering to include efforts to inject and store carbon dioxide in

aquifers , understanding certain types of volcanic eruptions, re-expansion of collapsed lungs, It may bring important knowledge in a wide range of fields, such as the development of better fuel cells. Papers that have not yet been peer-reviewed are posted on the preprint server arXiv.

in Science,   Junk Food, Posted by log1h_ik