Expanding on the principles of fluid dynamics

How liquids travel across, and through, surfaces is a heavily researched subject where new discoveries can have significant impacts on the fields of energy conversion technology, electronics cooling, biosensors and micro/nano-fabrications. Now, researchers from Kyushu University have used mathematical modelling and experimentation to expand on a fundamental principle in fluid dynamics. The new findings could lead to more efficient product development in liquid-based industries such as high-end electronics manufacturing and lab-on-a-chip disease diagnosis.

Assistant Professor Zhenying Wang said that in recent decades, scientists have made efforts to mathematically describe the phenomena of liquid flow and spreading. “For example, Tanner’s law describes how a droplet of water spreads on a solid surface over time,” Wang said.

However, these equations remain incomplete, with even Tanner’s law only valid for non-volatile liquids like oil. The law becomes less reliable when it comes to volatile liquids like water, alcohol and perfumes due to the thermodynamics between the air, liquid and surface coming into play.

“Therefore, we looked into the current laws in hopes of expanding our understanding of the dynamics of volatile liquids. We began by mathematically introducing parameters that reflect how volatile liquids react under similar conditions when Tanner’s law was derived,” Wang said.

The researchers then conducted a series of experiments imaging the movement and thermodynamics of volatile liquids. These two approaches allowed the researchers to scale up the established fluid dynamic principles and put together a more diverse picture of the physics of volatile liquids interacting with a surface and the air.

Associate Professor Chihiro Inoue said the research depicts a range of real cases and draws a more complete picture of liquid dynamics that could not be explained by Tanner’s law. “At a more practical level, these results could play a significant role in various liquid-based industries, for example in the cooling of electronics and other energy devices. The world of fluid dynamics can be very meticulous, but careful examination of it is required if we hope to decipher the fundamental flows around us,” Inoue said.

The research findings were published in the Journal of Fluid Dynamics.

Image credit: iStock.com/Elena Semenova