In the world of automotive engineering, lubricants play a crucial role in maintaining the health of a vehicle’s moving parts. The ability of these lubricants to flow, known as viscosity is a critical factor in their performance. However, recent research has revealed that there is an absolute cosmic limit to how viscous a fluid can be, far beyond what we encounter in everyday applications.
Masaki Yoshida, a professor at Japan’s Ritsumeikan University has published findings in the Physics of Fluids journal that define this upper limit. The study not only provides a concrete boundary for fluid dynamics but also offers insights into geological processes and the behavior of high-viscosity non-Newtonian fluids.
Defining the absolute cosmic limit of viscosity
The study defines the upper limit of viscosity as 1030±2 pascal-seconds (Pa s). To put this into perspective, water has a viscosity of approximately 10-3 Pa s while honey is around 101 Pa s. A material with such high viscosity flows so slowly that any measurable movement would exceed the age of the Earth. In practical terms, such a material is considered rigid.
Professor Yoshida’s research relied on decades of geodetic data, laboratory rock-deformation experiments, and simulations based on geological processes. The materials exhibiting the highest levels of viscosity are not typical lubricants but the building blocks of rocks, which flow when tectonic plates move. This research eliminates the placeholder of ‘infinite viscosity’ often used in fluid-dynamics studies, providing a concrete upper limit.
The implications of this discovery
The findings have significant implications for various fields. For researchers, it provides a clear boundary for fluid dynamics studies. The research also offers valuable insights into geologic activity, both past and present. Additionally, it can be useful in studying high-viscosity non-Newtonian fluids, such as ketchup, which change viscosity when subjected to force.
In the automotive world, understanding viscosity is crucial for developing effective lubricants. Dynamic viscosity for motor oils is typically measured in millipascal-seconds (mPa s), which is one-thousandth of a Pa s. The weight number on a bottle of motor oil is determined by measuring viscosity at multiple temperatures and creating an index from those measurements. This research reminds us that the same principles that keep our engines running also play a vital role in the geological processes that shape our planet.
