Have you ever wondered about the ''Teapot effect''?
When searching for a possible relation between teapots and science, I found an interesting paper dealing with the problem of dribbling teapots. In fact, everyone has experienced the annoying overflowing from the pot spout especially when the tea is poured slowly. Therefore I summarized the main points of this article and I also attached the link to download the full paper.
For centuries scientists have struggled to explain the ''teapot phenomenon''.Some suggested internal vortices in the fluid, others opted for atmospheric pressure as the main factor while other explanations based on the momentum of the fluid tried to find the perfect speed of the flow to avoid the dribbling.
A team of fluid dynamics scientists, C. Duez, C. Ybert, C. Clanet, and L. Bocquet, from the University of Lyon in France have addressed this issue by explaining the main factor of overflowing: a "hydro-capillary" effect that sticks the liquid to the solid surface as it is poured from the spout. The experts emphasised that to avoid this problem one way is to design the lip of the spout very sharp and coat the lip with superphobic materials to repel water from the spout. I reported below some pictures to explain the experiment :
In (a) when water leaves the spout of an (hydrophilic) teapot, the streamline bends and causes the dribbling , and this is worst at a slower flow rate(a').However, when using a superhydrophobic coating the streamline is straight and the dribbling problem is avoided at different flow rates b and b' .
