Intermittency and Solid-Fluid transition of Packed Grains

JC Tsai^1*, CE Tsai^2,1, WC Li¹, HC Fan-Chiang⁴, PY Hsiao³

¹Inst. of Physics, Academia *Taiwanica* (Academia Sinica, Taiwan), Taipei, Taiwan
²Physics, National Central University, Taoyan, Taiwan
³Engineering and System Science, NTHU, Hsin-Chu, Taiwan
⁴Physics, NTHU, Hsin-Chu, Taiwan

* Presenter:JC Tsai, email:jctsai@phys.sinica.edu.tw

Whether "granular flows" should be discussed in paradigms of "solids" or "fluids" is still up to debates. In this talk, we review both our laboratory works and an independent numerical experiment to address this long-standing issue. One published work [DoI: 10.1103/PhysRevLett.126.128001] reports the occurrence of a driving-rate dependent stick-slip intermittency as a distinctive signature of solid-fluid transition. With additional measurements on the tribology between particles [Tsai-CE, arXiv: 2010.07907], we identify the speed-dependent lubrication to be one fundamental cause for such transition, and propose a new dimensionless number as the control parameter on the change of behaviors. Numerical experiments [https://meetings.aps.org/Meeting/DFD21/Session/Q08.7] provide further insights beyond the restriction of laboratory experiments. These ongoing works allow us to generate and visualize the stick-slip intermittencies mimicking earthquakes which, to the best of our knowledge, have not been addressed in existing paradigms.

Keywords: granular, intermittent , solid-fluid transition, shear