Experimental Research Opportunity in Couette Flows of Granular Media

Prof. Martin Ostoja-Starzewski (martinos@illinois.edu) in the Department of Mechanical Science & Engineering has an experimental research opportunity on Couette flows of granular media.

For the last 35 years, physicists have been investigating spontaneous departures from the second law of thermodynamics via the Fluctuation Theorem [1] and Jarzynski equality [2]. While earlier studies focused on molecular systems, more recent works [3,4,5] have experimentally investigated such phenomena in granular media. The application of discrete computational dynamics methods (using the LAMMPS software) combined with statistical analysis has shown that the Fluctuation Theorem also applies to such macroscopic systems, even though they are characterized by non-Gaussian statistics and temporal profiles exhibiting fractal features and Hurst-type dependence. Experimental verification of these results remains a challenge. It is worth noting that, due to the rotation of the disks, the granular system constitutes an example of so-called "odd matter" with fluid-like properties [6].

It is necessary to complete the construction of the apparatus (already partially built at the Department of Mechanical Science & Engineering) to enable planar, frictionless flow of disks under general Taylor-Couette flow conditions on an air hockey-type apparatus with an annular geometry. The scope of work includes:

1. Preparing and testing the apparatus to ensure controlled flow (avoiding jamming or clogging) of the moving and colliding disks.

2. Configuration of a flow-measurement camera system enabling the tracking and recording of the individual velocities and rotations of the disks in the control window.

3. Replacement of homogeneous disks with composite disks, allowing for a detailed investigation of the gyroscopic effects involved.

4. Study jamming phenomena to determine how the avalanche statistics would change due to disks’ angular momenta. Also, analyze the data and extract the avalanche statistics. This research would be of particular interest to Prof. Karin Dahmen.

References:

1. Evans, D.J.; Searles, D.J. (2002) The Fluctuation Theorem. Advances in Physics 51, 1529–1585.

2. Jarzynski, C. (2011) Equalities and inequalities: irreversibility and the Second Law of thermodynamics at the nanoscale. Annu. Rev. Condens. Matter Phys. 2, 329--351.

3. Ostoja-Starzewski, M.; Laudani, R. (2020) Violations of the Clausius-Duhem Inequality in Couette Flows of Granular Media. Proc. Roy. Soc A 476: 20200207.

4. Laudani, R.; Ostoja-Starzewski, M. (2021) Spontaneous Negative Entropy Increments in Granular Flows. J. Appl. Mech. 88, 031010.

5. Wolfgram, Z.; Ostoja-Starzewski, M. (2024) Scaling, Fractal, and Hurst Effects in Spontaneous Violations of Entropy Inequality in Granular Couette Systems. Phys. Fluids 36, 073344.

6. Ostoja-Starzewski, M. (2026) Thermomechanics of Odd Matter: From Deterministic to Stochastic Media, New J. Physics 28, 063504.