Home Research paper US researchers study rod-shaped particles and provide modeling benchmark for future research

US researchers study rod-shaped particles and provide modeling benchmark for future research


From how to capture CO2 from the atmosphere to how to deliver vital drugs, scientists can answer a variety of questions by studying the movement of nanoparticles.

At the start of last month, university researchers published a study describing how nanoparticles move and disperse in flowing fluids. Assistant Professor of Engineering Daniel Harris was the Principal Investigator and worked with researchers Stuart Thomson, Ajay Harishankar Kumar ScM’20 and Professor of Engineering and Physics Thomas Powers.

“Historically, (our research) dates back to the work of mathematician GI Taylor,” said Thomson, a postdoc at Harris lab. Taylor’s work described how shear flow, which is a type of fluid flow induced by a pressure gradient, causes the dispersion and spreading of spherical nanoparticles, an effect known as Taylor’s dispersion. . This effect is very important in fluid dynamics, said Thomson.

“It’s easier to do analyzes and calculations on spherical particles, but in reality not everything is spherical,” said Kumar, who was the study’s first author. “In our study, we consider particles to be an ellipsoid or (a) long rod. We wanted to see what kind of effect the shape would have on the properties ”of the particles in the fluid, Kumar added.

To study the motion of ellipsoid-shaped particles, also called elongated rods, the researchers used a method known as Monte Carlo simulation – a type of computational algorithm that uses repeated random sampling. The researchers used the Oscar supercomputer at the Brown Computing and Visualization Center to run numerical simulations on nearly a million elongated particles subjected to shear fluid flow, Kumar said.

The Monte Carlo simulations took into account both the effect of fluid flow on elongated rods as well as Brownian motion, or the random motion of particles in the stagnant fluid, Thomson said. “There are differential equations you can model (particle motion) with,” he added.

After running the simulations, the researchers analyzed the speed of the particles. They also described the propagation of the particles, which they used to calculate a dispersion coefficient, Kumar said.

“We actually found that the rod-shaped particles propagated much more than the spherical particles in a high fluid flow rate,” Kumar said. The speed of the elongated rods appeared to decrease, but was statistically insignificant compared to the increase in the dispersion coefficient, he added.

Using the information from the simulations, the researchers were able to calculate a correction factor. “For actual applications… we can apply a small correction factor to the spherical housing and you get the rod-shaped housing,” Kumar said.

The simulation method and theoretical model in this study may provide a useful modeling reference for others in this area, Yun Chen, postdoctoral associate researcher at the University of Minnesota, wrote in an email to the Herald. “If we study similar particle systems… with different particle geometry, we could refer to this article and modify their model… to apply it to our own system,” added Chen, who was not involved in study.

Findings about the average speed and rate of rod dispersion may have applications to predict the behaviors of non-spherical biological objects, such as bacteria and microscopic health technology devices, he added.

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