Switching Flows in A 2D Silo*

We present experimental results on the flow of photoelastic particles in a quasi-2D silo with fixed circular intruders placed above the outlet.  We vary 1) the size of the intruder, 2) its placement, and focus on one outlet size. Our raw video data has high temporal and spatial resolution for particle tracking, and we use photoelastic particles to understand the force network. The intruders create multiple changes to the kinematic behavior, including but not limited to: increased/decreased bulk flow rate (compared to no intruder), differences in the microscopic particle motions, and switching flows, where one side flows faster than the other. Of particular interest is the nature of the switching flows, which have been deemed inscrutable in previous work and thus remain 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).