Kinetic particle simulations in a global toroidal geometry

Abstract Jamming/un-jamming, the transition between solid- and fluid-like behavior in granular matter, is an ubiquitous phenomenon in need of a sound understanding. As argued here, in addition to the usual un-jamming by vanishing pressure due to a decrease of density, there is also yield (plastic rearrangements and un-jamming that occur) if, e.g., for given pressure, the shear stress becomes too large. Similar to the van der Waals transition between vapor and water, or the critical current in superconductors, we believe that one mechanism causing yield is by the loss of the energy’s convexity (causing irreversible re-arrangements of the micro-structure, either locally or globally). We focus on this mechanism in the context of granular solid hydrodynamics (GSH), generalized for very soft materials, i.e., large elastic deformations, employing it in an over-simplified (bottom-up) fashion by setting as many parameters as possible to constant. Also, we complemented/completed GSH by using various insights/observations from particle simulations and calibrating some of the theoretical parameters—both continuum and particle points of view are reviewed in the context of the research developments during the last few years. Any other energy-based elastic-plastic theory that is properly calibrated (top-down), by experimental or numerical data, would describe granular solids. But only if it would cover granular gas, fluid, and solid states simultaneously (as GSH does) could it follow the system transitions and evolution through all states into un-jammed, possibly dynamic/collisional states—and back to elastically stable ones. We show how the un-jamming dynamics starts off, unfolds, develops, and ends. We follow the system through various deformation modes: transitions, yielding, un-jamming and jamming, both analytically and numerically and bring together the material point continuum model with particle simulations, quantitatively. Graphic abstract

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Continuity waves in resolved-particle simulations of fluidized beds

Physical Review Fluids ◽

10.1103/physrevfluids.2.114305 ◽

2017 ◽

Vol 2 (11) ◽

Cited By ~ 4

Author(s):

Daniel P. Willen ◽

Adam J. Sierakowski ◽

Gedi Zhou ◽

Andrea Prosperetti

Keyword(s):

Fluidized Beds ◽

Particle Simulations

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Particle simulation of plasmons

Nanophotonics ◽

10.1515/nanoph-2020-0067 ◽

2020 ◽

Vol 9 (10) ◽

pp. 3303-3313 ◽

Cited By ~ 1

Author(s):

Wen Jun Ding ◽

Jeremy Zhen Jie Lim ◽

Hue Thi Bich Do ◽

Xiao Xiong ◽

Zackaria Mahfoud ◽

...

Keyword(s):

Simulation Method ◽

Electron Excitation ◽

Particle Simulation ◽

Quantum Limit ◽

Free Electrons ◽

Theoretical Approaches ◽

Electromagnetic Responses ◽

Electric And Magnetic Fields ◽

Particle Simulations ◽

Collective Oscillations

AbstractParticle simulation has been widely used in studying plasmas. The technique follows the motion of a large assembly of charged particles in their self-consistent electric and magnetic fields. Plasmons, collective oscillations of the free electrons in conducting media such as metals, are connected to plasmas by very similar physics, in particular, the notion of collective charge oscillations. In many cases of interest, plasmons are theoretically characterized by solving the classical Maxwell’s equations, where the electromagnetic responses can be described by bulk permittivity. That approach pays more attention to fields rather than motion of electrons. In this work, however, we apply the particle simulation method to model the kinetics of plasmons, by updating both particle position and momentum (Newton–Lorentz equation) and electromagnetic fields (Ampere and Faraday laws) that are connected by current. Particle simulation of plasmons can offer insights and information that supplement those gained by traditional experimental and theoretical approaches. Specifically, we present two case studies to show its capabilities of modeling single-electron excitation of plasmons, tracing instantaneous movements of electrons to elucidate the physical dynamics of plasmons, and revealing electron spill-out effects of ultrasmall nanoparticles approaching the quantum limit. These preliminary demonstrations open the door to realistic particle simulations of plasmons.

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