Intruder Effects in a 2D Silo

We present experimental results on the flow of particles in a quasi-2D silo with fixed circular intruders placed above the outlet. Our raw video data has high temporal and spatial resolution for particle tracking. Additionally, our particles are photoelastic, and so we can characterize the contact forces in the system. We seek to quantify how these interaction forces influence the kinetic behavior of the system, such as bulk flow and local rearrangements. Of particular interest in intruder systems is switching flows. During a single flow experiment, sometimes the flow is even on both sides of the intruder, sometimes the particles flow more on the left or right side. This aperiodic switching between states has been deemed inscrutable in previous work and thus remains ill-quantified [1-2]. We present quantitative metrics of this switching as a function of intruder size and position.

​​[1] A. B. Harada, E. Thackray, and K. N. Nordstrom, Phys. Rev. Fluids 7, 054301 (2022).

[2] K. Endo, K. A. Reddy, and H. Katsuragi, Phys. Rev. Fluids 2, 094302 (2017).