Crushed artificial stones help solve the mystery of 54 years old

Princeton researchers have developed a technique to better understand how polymers flow through small channels under pressure. Credit: David Kelly Crow

Princeton researchers have solved a 54-year-old puzzle about why certain fluids are strangely slow under pressure when flowing through porous materials such as soil and sedimentary rocks. The findings could help improve many important processes in the energy, environmental and industrial sectors, from oil recovery to groundwater purification.

The fluid in question is called polymer solution. These solutions (daily examples include cosmetic creams and nasal mucus) include materials made of dissolved polymers or large molecules with many repeating subunits. Normally, when pressure is applied, the viscosity of the polymer solution decreases, flow Faster. However, when passing through materials with many small holes and channels, the solution is more viscous, tends to be ganky, and has a reduced flow rate.

To find the root of the problem, Princeton researchers devised an innovative experiment using clear artificial stone, a see-through porous medium made of small glass beads. This transparent medium allowed researchers to visualize the movement of polymer solutions. Experiments have shown that a long and mysterious increase in the viscosity of a porous medium causes the flow of polymer solution to become disordered, like eddy when boarding an airplane, swirling itself and gumming the work. It became clear that it would occur.

“Surprisingly, it was not possible to predict the viscosity of a polymer solution flowing through a porous medium,” said a study published on November 5, an assistant professor of chemistry and biotechnology at Princeton University. Said Sujit Datta, senior author of.journal Science Advances.. “But this paper finally shows that these predictions are possible, so we have found answers to problems that researchers have not understood for more than half a century.”

“This study has finally made it possible to see exactly what is happening underground or in other opaque porous media when the polymer solution is being pumped,” he said. Christopher Brown, who obtained the issue, said. A student in Datta’s lab and the lead author of the dissertation.

Brown ran the experiment and built the experimental equipment. This is a small rectangular chamber randomly packed with small borosilicate glass beads. The artificial sedimentary rock-like setup was only about half the length of the little finger. On this throat rock, Brown pumped a common polymer solution mixed with fluorescent latex particles and checked the flow of the solution around the beads. Researchers have formulated a polymer solution so that the index of refraction of the material offsets the distortion of light from the beads and makes the entire setup transparent when saturated. Datta’s lab used this technique in an innovative way. See-through soil To study ways to combat agricultural drought Other surveys..

Brown then magnified the pores or holes between the beads under a microscope. These holes are 100 micrometers (one millionth of a meter) in size, or resemble the width of a human hair. Fluid flow Through each pore. As the polymer solution passed through the porous medium, the fluid flow became disordered and the fluid collided with itself, creating turbulence. Surprisingly, fluids usually flow at these velocities, a “laminar flow” rather than a turbulent flow within such narrow pores, and the fluid moves smoothly and steadily. However, as the polymer moved through the pore space, the polymer stretched and generated force, accumulating and creating turbulence in the various pores. This effect became more pronounced when the solution was extruded at higher pressure.

“We were able to identify and record all of these unstable spotted areas, which have a significant impact on the transport of solution through the medium,” says Brown.

Crushed artificial stones help solve the mystery of 54 years old

Princeton researchers have developed a technique to better understand how polymers flow through small channels under pressure. Credit: David Kelly Crow

Princeton researchers have used data collected from experiments to develop ways to predict the behavior of polymer solutions in real-world situations.

Gareth McKinley, a professor of mechanical engineering at the Massachusetts Institute of Technology who was not involved in the study, provided comments on its importance.

“This study shows that the macroscopically observable increase in pressure drop across the porous medium has a microscopic physical origin in the instability of the viscoelastic flow that occurs on the pore scale of the porous medium. It’s a clear indication, “says McKinley.

Given that viscosity is one of the most basic descriptors of fluid flow, the findings not only help to better understand general polymer solution flow and chaotic flow, but also in the field. It also provides quantitative guidelines for providing information to large-scale applications.

“The new insights we have created can help practitioners in different situations decide how to prescribe the right polymer. Solution “We will use the appropriate pressure needed to carry out the task at hand,” said Datta. “We are particularly excited to apply the findings in groundwater purification.”

Because polymer solutions are inherently sticky, environmental engineers inject the solution into the ground in highly polluted areas such as waste chemical plants and industrial plants. Viscous solutions help push traces of contaminants out of the affected soil. Polymer solutions also help oil recovery by pushing oil out of the pores of underground rocks. In terms of restoration, polymer solutions allow for “pump and treat”. This is a common method for purifying groundwater contaminated with industrial chemicals and metals, including transporting the water to a surface treatment station. “All these uses of polymer solutions, as well as other uses such as separation and manufacturing processes, will benefit from our discoveries,” says Datta.

as a whole, Polymer solution Flow rate Porous medium He put together ideas from multiple disciplines of scientific research and eventually unraveled what began as a long, frustrating and complex problem.

“This study draws a link between polymer physics, turbulence, and earth science studies, following the flow of fluid through underground rocks and aquifers,” said Datta. “It’s a lot of fun sitting on the interface between all these different disciplines.”

Small polymer springs boost environmental cleanup

For more information:
Christopher A. Browne et al, elastic turbulence creates anomalous flow resistance in a porous medium. Science Advances (2021). DOI: 10.1126 / sciadv.abj2619..

Quote: The crushed artificial stone is a 54-year-old mystery (2021) obtained from on November 5, 2021. Helps to decipher (November 5, 2014)

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Crushed artificial stones help solve the mystery of 54 years old

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