The inner workings of puddles don't exactly sound like ground-breaking science, but researchers from MIT beg to differ. In a study published in the journal Physical Review Letters, they detailed the physics behind puddle behavior — pointing out a number of applications the discovery could benefit.
When water is spilled, a puddle spreads but stops — ending with a well-defined pool of water. The problem is, scientific formulas for explaining fluid flow dictate that the water should keep spreading. Ruben Juanes, Amir Pahlavan, Luis Cueto-Felgueroso and Gareth McKinley sought to understand why puddles deviate from the norm and found that molecular forces are at play.
According to Pahlavan, the classic thin-film model used by scientists doesn't predict that fluid will stop. He added that forces responsible for impeding fluid flow only show up at the molecular level. Minuscule though they may be, the forces have enough effect to affect the behavior of liquid. Beyond the molecular level, though, it isn't obvious what keeps a puddle from flowing.
Pahlavan explained that liquid-air and liquid-solid interfaces can be found close to the edge of the puddle. These interfaces interact with each other and these interactions account for the missing intermolecular forces that prevent a puddle from spreading endlessly.
How does knowing the role nanoscale physics plays in keeping a puddle steady benefit anyone?
Among other things, the researchers said that a better understanding of liquid behavior can aid in figuring out how much oil a gear train needs to run without trouble, or how much drilling "mud" an oil rig will require to keep working smoothly. The findings from the study can also impact microchip design, by helping develop liquid cooling systems that will keep chips from overheating.
The study explored puddle behavior on perfectly smooth surfaces, so the next step for the researchers will be to assess their findings using fluid on rougher surfaces.
"This work puts us in a position to be able to better describe multiphase flows in complex geometries like rough fractures and porous media," said Juanes.
Juanes is an environmental and civil engineering professor from MIT, while Pahlahvan is a graduate student. Cueto-Felgueroso is a research associate in the university and McKinley is a mechanical engineering professor.
This study received support from the U.S. Department of Energy.
