3rd Regular Kakenhi Meeting
"Theoretical studies of non-equilibrium driven-dissipative systems"
Date: Nov. 8th, 2023
Hybrid meeting: onsite (K206, YITP, Kyoto Univ.) & online
| Presentation Time | Speaker |
|---|---|
| 09:30—10:00 | Hisao Hayakawa† (YITP, Kyoto Univ.) "Theory of Mpemba effect: quantum and classical" (abstract)I briefly explain the essence of Mpemba effect using models of quantum Mpemba effects and classical models. |
| 10:00—10:30 | Ryosuke Yoshii‡ (Sanyo-Onoda City Univ.) "Geometric engine in nonequilibrium system" (abstract)Under the parameter modulation, the state of the system can be different from the nonequilibrium steady state defined by the zero eigenmode of the Liouvillian. We show the geometric interpretation of the state (referred to as the geometric state) under the parameter modulation and the relaxation process towards the geometric state can be utilized to realize the engine. |
| 10:30—10:50 | break |
| 10:50—11:20 | Pradipto† (Tokyo Univ. Agri. Tech.) "Effective viscosity and elasticity in dense suspensions under impact" (abstract)The elastic response of dense suspensions under an impact is studied using coupled lattice Boltzmann method and discrete element method (LBM-DEM) and its reduced model. We succeed to extract the elastic force acting on the impactor in dense suspensions, which can exist even in the absence of percolating clusters of suspended particles. We then propose a reduced model to describe the motion of the impactor and demonstrate its relevancy through the comparison of the solution of the reduced model and that of LBM-DEM. Furthermore, we illustrate that the perturbation analysis of the reduced model captures the short-time behavior of the impactor motion quantitatively. |
| 11:20—11:50 | Hirokazu Maruoka† (YITP, Kyoto Univ.) "Dynamical response of a suspension of mili-order particles against a falling rigid sphere" (abstract)In this study, we discuss the dynamical response of a suspension of mili-order particles, of which Reynolds number is expected to be high and it was expected to reveal different response from the typical suspension of micro-order particles. We did the experiment of falling rigid sphere on a suspension and estimated the drag force by using event-base camera. Interetingly, it was found that the response was largely following the floating model which was applied to the suspension of low Reynolds number. It might be originated from the high effective viscosity of dense suspensions, which leads to small effective Re even if we use large suspended particles. |
| 11:50—13:30 | break |
| 13:30—15:00 | Tapan Sabuwala (OIST) "Using granular models to investigate regolith distribution on planetary surface" (abstract)Morphological features of planetary bodies often serve as key pieces of forensic evidence that allow us to piece togather their formation and evolution. These features are shaped by the movement of regolith, loose debris that forms the surface layer of planetary bodies. In this talk, I will showcase different projects where we use simple ideas from granular physics to model regolith distribution on planetary surfaces, such as the asymmetric distribution of material ejected during the formation of impact craters [1], size-based segregation on the asteroid Itokawa [2], and the role of centrifugal forces in regolith distribution on spinning asteroids [3]. When possible, we recreate observed morphological features using experiments and particle-based simulations to track the underlying mechanism. Apart from previously published research, I will also discuss some ongoing projects that might serve as grounds for possible collaboration.[1] Sabuwala, T., Butcher, C., Gioia, G., and Chakraborty, P. (2018). Ray systems in granular cratering. Physical Review Letters, 120(26), 264501. [2] Shinbrot, T., Sabuwala, T., Siu, T., Lazo, M. V., and Chakraborty, P. (2017). Size sorting on the rubble-pile asteroid Itokawa. Physical review letters, 118(11), 111101. [3] Sabuwala, T., Chakraborty, P., and Shinbrot, T. (2021). Bennu and Ryugu: diamond in the sky. Granular Matter, 23, 1-5. |
| 15:00—15:30 | break |
| 15:30—16:00 | Kuniyasu Saitoh† (Kyoto Sangyo Univ.) "Sound damping near jamming: the difference between stressed and unstressed systems" (abstract)We study sound properties of soft athermal particles near jamming. Numerically demonstrating elastic waves of the particles, we show that time correlations of particle velocities are dampened by both disordered configuration of the particles and energy dissipation due to contact damping. We extract sound characteristics such as dispersion relations, sound speeds, and attenuation coefficients from the results of velocity auto-correlation functions and find that these are strongly dependent on the proximity to the jamming transition. We connect the sound speeds and attenuation coefficients to complex moduli of soft athermal particles on the basis of linear viscoelasticity. Then, we explain the critical behavior of sound characteristics near jamming by the critical scaling of complex moduli, where we put great emphasis on the difference between stressed and unstressed states of the particles. |
| 16:00—16:30 | Satoshi Takada† (Tokyo Univ. Agri. Tech.) "Revisiting the kinetic theory for moderately dense granular flows" (abstract)We revisit the kinetic theory for moderately dense granular flows based on recent developments. We show that our theory works for below the Alder transition point. We discuss the applicability of theory for large inelastic regime, where the previous theory [1], which was originally derived for homogenous cooling states, cannot capture the behavior.[1] V. Garzó and J. W. Dufty, Phys. Rev. E 59, 5895 (1999). |
| 16:30—17:00 | Michio Otsuki† (Osaka Univ.) "Static Friction Coefficient Depends on the External Pressure and Block Shape due to Precursor Slip" (abstract)Amontons' law states that the maximum static friction force on a solid object is proportional to the loading force and is independent of the apparent contact area. This law indicates that the static friction coefficient does not depend on the external pressure or object shape. Here, we numerically investigate the sliding motion of a 3D viscoelastic block on a rigid substrate using the finite element method (FEM). The macroscopic static friction coefficient decreases with an increase in the external pressure or shape of the object, which contradicts Amontons' law. Precursor slip occurs in the 2D interface between the block and the substrate before bulk sliding. The decrease in the macroscopic static friction coefficient is scaled by the critical area of the precursor slip. A theoretical analysis of simplified models reveals that bulk sliding results from the instability of the quasi-static precursor slip caused by velocity-weakening local friction. We theoretically predict the dependence of the critical area and the macroscopic static friction coefficient on the pressure or shape of the object [1, 2]. The validity of the theoretical prediction is numerically confirmed.[1] W. Iwashita, H. Matsukawa, and M. Otsuki, Sci. Rep. 13, 2511 (2023). [2] W. Iwashita, H. Matsukawa, and M. Otsuki, arXiv:2309.08111. |
| 17:00—17:20 | break |
| 17:20—17:50 | Shihori Koyama† (Toyota Central R&D Labs.) "Vibrations in granular solids driven by random forces" (abstract)It is well known that the law of equipartition of energy holds in thermal equilibrium systems, but it is not trivial in dissipative systems. In this study, we investigate the vibrational properties in granular systems with particular attention to the differences in dissipation mechanisms. The kinetic energy distributed to each vibrational mode is obtained for dense granular systems in which particle velocity-dependent dissipation and random forces are at work. The result shows that when the dissipation acts on relative velocities, the law of equipartition of energy is violated and lower frequency modes are emphasized. This means that more cooperative vibration characteristics emerge in such systems. |
| 17:50—18:20 | Grzegorz Szamel† (Colorado State Univ.) "Sound attenuation in glasses" (abstract)Sound attenuation in low temperature amorphous solids originates from their disordered structure. However, its detailed mechanism is still being debated. I will present an analysis of sound attenuation starting directly from the microscopic equations of motion. I will show that the new expressions for the zero-temperature sound damping coefficients agree very well with the results of independent, direct simulations of sound attenuation. |