Modeling the Properties of Granular Materials

Emma Thackray '18, Student Researcher

Major: Physics

Research Group: The Nordstrom Lab

Emma Thackray has been working in Professor Kerstin Nordstrom's lab since the Spring of 2015. Her project is on the behavior of flowing granular material, like sands through an hourglass. "Think of a sink of marbles under light," she says. "Using the sensitive camera we have in the lab, which can take thousands of frames per second, we can zoom in and observe the properties of granular materials."

The granular system she is studying consists of special ‘photoelastic’ particles. The system is placed between two polarizing sheets, which would normally block out all light. But as Thackray says, "As these materials shift and roll over one another, the forces in the system change, altering the characteristics of the system, including the way the grains transmit light."

The upshot is that particles experiencing large forces appear bright because they transmit light, particles not under stress block out light. (In technical terms, the force induces birefringence in the material.) Using the high-speed camera, they can then directly visualize the force network within the system, and image forces as they are transmitted in real time. With this data she can begin to “model the properties of granular materials.”