Robert P. Behringer
, James B. Duke Professor of Physics, received his PhD from Duke University in 1975. His postdoctoral research was at Bell Laboratories in Murray Hill, NJ. He was an assistant professor at Wesleyan University in Middletown, CT from 1977-1982 and has been a professor at Duke University since 1982. He has secondary appointments in Computer Science, Mechanical Engineering, and Material Sciences. Click here for his home page
In his spare time, Bob likes to do science outreach with the community. Click here
to see some of his recent adventures. Bob has recently taken on the challenge of vice-chairing and then chairing a topical group with APS on the physics of climate. The goal of the group is to analyze climate science in a way that is completely divorced from political and societal points of view. Click here
to read more.
Joshua A. Dijksman received his PhD from Leiden University, the Netherlands, in December 2009. He has worked on compaction of granular materials, slow and fast granular flows in the split-bottom geometry, and the rheology and three dimensional imaging of dense suspensions. He joined the Behringer group as a postdoc in early 2010.
Nicolas Brodu received his PhD in computer science from Concordia University, Canada, in June 2007. His main interest is how to deal with complex systems, which he applied on different contexts: artificial intelligence, brain- computer interfaces, geomorphology and granular matter physics. He showed new flow regimes for channeled granular matter and then joined the Behringer group in October 2012 as a postdoc. He has since worked on how to measure forces in full 3D inside granular materials and how to track the evolution of their structure over time during shear or compression cycles.
Abe Clark is a PhD student who has an MSEE from Texas Tech, where his primary research was in charged particle optics and photomultiplier tube design. He started at Duke in August, 2008. His thesis project at Duke focuses on the dynamics of granular impact. By using photoelastic disks and a high-speed camera, he studies particle-scale mechanisms which are responsible for the loss of energy by an intruder as it impacts the granular material and comes to a stop. Additionally, he has worked on a project studying the dynamics of crater formation by a jet of gas impinging on a granular bed, as well as a project which models industrial granular impeller-mixers.
Dong Wang earned his B.S. from the University of Science and Technology of China. He came to Duke in 2012 to earn his PhD.
Jenny Su is a third-year undergraduate major in Physics. In the Behringer lab, her research involves studying the dual properties of bouncing droplets on a vertically vibrating bath to create a macroscopic model of quantum behavior.
Melodie Lim Can you walk on water? The obvious answer is, of course not. But what if some cornstarch is thrown into the water? It turns out that under certain specific circumstances, such as large forces (as demonstrated in recent experiments available on YouTube), a mixture of cornstarch in water will be as rigid as a solid. Interestingly, however, the behavior of these suspensions is strongly dependent on the fluid out of which they are composed. Melodie Limʼs work in the Behringer lab involves finding a way to quantify the difference between suspensions in different fluids, and therefore to investigate the effects that the microstructure of a suspension have on its macroscopic mechanical behavior. Microstructure is arrangement in space of the grains of cornstarch or other very small suspended particles. Microstructure is important because it provides the mechanism for ʽwalking on waterʼ, that is supporting weight in a way that is similar to a solid, but with a fluid-like system. Melodie is an undergraduate Physics major at Duke.
Email: email@example.com Telephone: 919.660.2553
Alec Petersen has been extensively involved in studies of impact on granular materials. Our group has used circular intruders to study impacts on granular 'beds' that consist of photoelastic particles. These experiments use very fast video imaging that captures the fastest microscopic processes involved in the impact. Based on these data, we have developed collisional force-law models of granular impact. In Alec's work, we particularly focused on experiments for impacts of triangular-shaped intruders, and we then used these data to test and better understand a collisional model for impacts. Intruders with triangular-noses are particularly useful because the calculation of the collision term in our model becomes very simple. An additional interesting feature of the triangular intruders that Alec uses is that they may spontaneously rotate. This rotation is often unstable, i.e., once the intruder tilts a bit from vertical, the angular velocity associated with the intruder increases quickly. In fact, the experimental data for intruders that rotate reveal an exponential relationship between the angle of rotation and the depth of the intruder. This novel finding helped us further develop our microscopic picture. This model addresses both the stopping force experienced by the intruders, and the torque that they experience. Alec is an undergraduate Physics major at Duke.
Audrey Melville investigates the disparity in observed jamming effects of suspensions of different types of particles that are similar in size and shape. She is working to understand how the rates at which different particles in a suspension either cream to the top or settle to the bottom are related to the observed jamming phenomenon of these suspensions. Work during the summer of 2013 involved taking time-lapsed photographs of these processes and analyzing the particle dynamics from the series of images for each suspension. She generated data that tracks the dynamics of the various suspensions as they cream/settle, and from that extracted the velocities for these processes. On comparing these processes, even after scaling out the density difference between the particles and surrounding fluid (the only factor that should contribute to a difference in creaming/settling velocity) the dynamics do not match for different types of comparably-sized particles, indicating that the details of inter-particle interactions could cause differences in jamming behavior.
Email: Telephone: 919.660.2553
A group shot in front of the Duke chapel.