TY - JOUR
T1 - Enstrophy cascades in two-dimensional dense granular flows
AU - Saitoh, Kuniyasu
AU - Mizuno, Hideyuki
N1 - Funding Information:
We thank H. Hayakawa, M. Otsuki, and T. Kawasaki for fruitful discussions. This work was financially supported by World Premier International Research Center Initiative (WPI), Ministry of Education, Culture, Sports, Science, and Technology, Japan (MEXT), and Kawai Foundation for Sound Technology & Music. This work was also supported by Grant-in-Aid for Scientific Research B (Grants No. 16H04025 and No. 26310205) from the Japan Society for the Promotion of Science (JSPS). A part of the numerical computations has been carried out at the Yukawa Institute Computer Facility, Kyoto, Japan.
Publisher Copyright:
© 2016 American Physical Society.
PY - 2016/8/31
Y1 - 2016/8/31
N2 - Employing two-dimensional molecular dynamics simulations of dense granular materials under simple shear deformations, we investigate vortex structures of particle rearrangements. Introducing vorticity fields as a measure of local spinning motions of the particles, we observe their heterogeneous distributions, where statistics of vorticity fields exhibit the highly non-Gaussian behavior and typical domain sizes of vorticity fields significantly increase if the system is yielding under quasistatic deformations. In such dense granular flows, a power-law decay of vorticity spectra can be observed at mesoscopic scale, implying anomalous local structures of kinetic energy dissipation. We explain the power-law decay, or enstrophy cascades in dense granular materials, by a dimensional analysis, where the dependence of vorticity spectra not only on the wave number, but also on the shear rate, is well explained. From our dimensional analyses, the scaling of granular temperature and rotational kinetic energy is also predicted.
AB - Employing two-dimensional molecular dynamics simulations of dense granular materials under simple shear deformations, we investigate vortex structures of particle rearrangements. Introducing vorticity fields as a measure of local spinning motions of the particles, we observe their heterogeneous distributions, where statistics of vorticity fields exhibit the highly non-Gaussian behavior and typical domain sizes of vorticity fields significantly increase if the system is yielding under quasistatic deformations. In such dense granular flows, a power-law decay of vorticity spectra can be observed at mesoscopic scale, implying anomalous local structures of kinetic energy dissipation. We explain the power-law decay, or enstrophy cascades in dense granular materials, by a dimensional analysis, where the dependence of vorticity spectra not only on the wave number, but also on the shear rate, is well explained. From our dimensional analyses, the scaling of granular temperature and rotational kinetic energy is also predicted.
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U2 - 10.1103/PhysRevE.94.022908
DO - 10.1103/PhysRevE.94.022908
M3 - Article
AN - SCOPUS:84989352438
VL - 94
JO - Physical Review E
JF - Physical Review E
SN - 2470-0045
IS - 2
M1 - 022908
ER -