Kinetic theory of discontinuous shear thickening

A simple kinetic theory to exhibit a discontinuous shear thickening (DST) is proposed. The model includes the collision integral and the friction from environment as well as a thermostat term characterized by $T_{\rm ex}$. The viscosity of this model is proportional to $\dot\gamma^2$ for large shear rate $\dot\gamma$, while it is Newtonian for low $\dot\gamma$. The emergence of the DST is enhanced for lower density and lower nonzero $T_{\rm ex}$.Comment: 4 pages, 2 figures, Powders and Grains 2017 (in press

Particle flows around an intruder

Particle flows injected as beams and scattered by an intruder are numerically studied. We find a crossover of the drag force from Epstein's law to Newton's law, depending on the ratio of the speed to the thermal speed. These laws can be reproduced by a simple analysis of a collision model between the intruder and particle flows. The crossover from Epstein's law to Stokes' law is also found for the low-speed regime as the time evolution of the drag force caused by beam particles. We also show the existence of turbulent-like behavior of the particle flows behind the intruder with the aid of the second invariant of the velocity gradient tensor and the relative mean square displacement for the high-speed regime and a large intruder.Comment: 10 pages, 13 figure

Pattern dynamics of cohesive granular particles under a plane shear

We perform three dimensional molecular dynamics simulations of cohesive granular particles under a plane shear. From the simulations, we found that the granular temperature of the system abruptly decreases to zero after reaching the critical temperature, where the characteristic time $t_{\rm cl}$ is approximately represented by $t_{\rm cl} \propto (\zeta-\zeta_{\rm cr})^{-\beta}$ with the dissipation rate $\zeta$, the critical dissipation rate $\zeta_{\rm cr}$ and the exponent $\beta \simeq 0.8$. We also found that there exist a variety types of clusters depending on the initial density and the dissipation rate.Comment: 4 pages, 5 figure

Kinetic theory for dilute cohesive granular gases with a square well potential

We develop the kinetic theory of dilute cohesive granular gases in which the attractive part is described by a square well potential. We derive the hydrodynamic equations from the kinetic theory with the microscopic expressions for the dissipation rate and the transport coefficients. We check the validity of our theory by performing the direct simulation Monte Carlo.Comment: 22 pages, 11 figure