The teapot party wet/dry
Teapot technology is largely ignored by mainstream media (some say unfairly). But today, scientists in France unveil a technique that should breath hi-tech life into a new generation of bespouted objects.
The problem with teapots is their annoying habit of dribbling, particularly at low rates of flow. The phenomenon has achieved such notoriety that it has been imaginatively dubbed the “teapot effect”.
Previous studies have shown that dribbling is the result of flow separation where the layer of fluid closest to the boundary becomes detached from it. When that happens, the fluid flows smoothly over the lip. But as the flow rate decreases, the boundary layer re-attaches to the surface causing dribbling.
Previous studies have shown that a number of factors effect this process such as the radius of curvature of the teapot lip, the speed of the flow and the “wettability” of the teapot material. But a full understanding of what’s going on has so far eluded scientists.
Now Cyril Duez at the University of Lyon in France and a few amis, have identified the single factor at the heart of the problem and shown how to tackle it. They say that the culprit is a “hydro-capillary” effect that keeps the liquid in contact with the material as it leaves the lip. The previously identified factors all determine the strength of this hydro-cappillary effect.
