When Associate Professor Nathalie Vriend was named a 2023 Experimental Physics Investigator by the Gordon and Betty Moore Foundation, a highly prestigious award in the experimental physics community, the foundation invited her to attend their annual conference. But she had to decline – she was in the middle of hiking the 567-mile Colorado Trail with her family.
She’ll be there next year, though. The funding provides five years of support for her research, which is itself inspired by her love of nature.
The Moore Foundation’s Experimental Physics Investigators Initiative supports experimental physicists to tackle their most creative research ideas. Vriend will receive $1.25 million from the foundation to further her innovative research in granular flows in the natural environment.
In her laboratory experiments, Vriend uses a technique called photoelasticity that analyzes how patterns of light within particles change according to the magnitude and direction of forces exerted upon them. The changing patterns of light can give Vriend a picture of the stress distribution between particles in situations like rockslides or cereals flowing out of a grain silo.
“We can measure how these tiny particles flow,” Vriend said, “and understand their acceleration and velocity and create models of their movement.”
With the funding from the Moore Foundation, Vriend plans to take her research to another level. So far, Vriend has focused on dry granular flows, like sand or snow, but now she wants to introduce fluid between the particles. In addition to the solid contact forces already exerted onto the particles, this would add hydrodynamic stresses as well.
“If you think about fluids like water, they behave in a certain way. We call it Newtonian. If you stress it harder, then it will resist harder, and it's very linear,” Vriend said. “But if you insert particles, it changes the fluids in a nonlinear way. And it makes it very difficult to model.”
The scientific community is completely in the dark about how particles function within particle-fluid states of matter, which are called “suspensions,” like mudslides or lava flows. Vriend’s research presents a unique opportunity to characterize suspensions by quantitatively measuring and modeling their interactions.
Ultimately, Vriend’s work has the potential to advance the analysis, modeling, and predicting of natural hazards like landslides, avalanches or ice formations.
“I love to work from nature,” said Vriend, who considers herself chiefly a mechanical engineer but versed in geophysics as well. At Cambridge University, Vriend spent nine years in the applied math department, where she worked on fluid dynamics before moving to the earth science department for three years.
For someone like Vriend who enjoys nature, Colorado is good place to be.