Drexel University researchers have found that water can break down like solids under certain conditions. In a discovery that could revolutionize our understanding of fluid mechanics, it now appears that viscous fluids can suddenly break when stretched with sufficient force.
Unlike solids, which will stretch and eventually break, water has never been believed to have a breaking point. However, this new research seems to challenge this belief.
“Our research shows that if they are separated by enough force at each point, a simple fluid – a flowing fluid – will reach a point where we call it ‘high stress,’ in fact it will break like a solid,” said Thamires Lima, Ph.D., assistant professor in the College of Engineering, Drexel’s College of Engineering, who helped lead the research.
Interestingly, the team also discovered that the “snapping” fluid produces a sudden noise, like breaking solids. There is no doubt that this was also unexpected.
“What we saw was so unexpected that we had to repeat the experiment several times to make sure it was true,” explains Nicolas Alvarez, Ph.D., a professor in the College of Engineering whose lab led the research.
“Once we confirmed this phenomenon, the investigation became a completely different scientific endeavor,” he added.
Liquids can spoil after all
“This was really amazing to see,” Lima said. He said: “The break made a very loud noise which scared me.
The key to the research is that fluids will fracture in this way if they are separated at a speed that prevents them from “flowing” under stress. As in solids, this allows enough time for the stress to build up enough for a sudden fracture to form.
From the tests, the team found that the drinks tend to break at about 2 megapascals of tension. The exact number, of course, depends on the fluid’s viscosity (thickness).
The higher the viscosity, the more likely it is to appear explosive. “This is likely to be true for simple liquids, including common examples, such as water and oil… This changes our understanding of fluid dynamics,” he added.
“Although viscoelastic and polymer liquids – things like Oobleck or artificial slime – have shown solid behavior like breaking, soft water has always been thought to show a change in temperature above their glass transition and therefore will not break,” Lima said.
As for what this means for the real world outside the lab, it could open up some interesting lines of research in various industries. “Showing that viscous effects are sufficient to promote solid behavior such as fracture opens up a world of new questions to be explored in this area of scientific research,” he said.
Interesting possibilities for future study
For example, 3D printing, which uses water polymers, can benefit from a better understanding of water’s fracture limits. Making fibers, which tend to stretch water into fibers, can obviously also benefit from such knowledge.
In medical science, things like blood (which are liquids) could be investigated to see that they break in certain conditions and to find ways to avoid them. Hydraulics can also be another interesting area of study.
“This suggests that many other liquids can also break down at a similar time to stress,” Lima added. He explains: “This points to a phenomenon that is almost chemically independent and may be common to many types of water.
Another interesting area of study would be cavitation from ship or submarine propellers, pumps, and other sonar equipment. Here, tiny bubbles form and collapse violently, which can damage metals, create shock waves, and create noise.
With a better understanding of the physics involved, it may be possible to reduce or eliminate cavitation problems in the future.
“Now that we have documented this unexpected behavior, the work to fully understand why it occurs and how the behavior manifests itself in other beverages is an important next step,” Lima said. He added: “It will also be interesting to see how this result can be used to aid fiber spinning and other processes that use viscous liquids.”
You can see the study yourself in the journal Physical Examination Letters.
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