A coupled Particle-In-Cell (PIC)-Discrete Element Method (DEM) solver for fluid-solid mixture flow simulations

In this paper, a coupled Particle-In-Cell (PIC)-Discrete Element Method (DEM) model is developed for numerical simulations of complex fluid–solid mixture flows. The fluid–solid interaction part is solved using the hybrid Eulerian–Lagrangian PIC model, and the solid–solid interaction part is simulated using the Lagrangian DEM model. The PIC model gives the coupled PIC-DEM model both Eulerian efficiency and Lagrangian flexibility, compared to purely Lagrangian methods such as Smoothed Particle Hydrodynamics (SPH). The time step difference between the PIC model and the DEM model is handled using the idea of subcycles. In addition, a straightforward method is proposed for mitigating the issue of unphysical gaps between solids during collision due to the use of the Cartesian cut cell method for fluid–solid interaction. The PIC-DEM model is validated by physical experiments of the collapse of solid cylinder layers with and without water. Following that, the capability of the numerical model is further demonstrated through a more complex problem of solid dumping through fall pipes. The results show great potential of the PIC-DEM model being a useful tool for simulating complex fluid–solid mixture flows

A coupled Particle-In-Cell (PIC)-Discrete Element Method (DEM) solver for fluid-solid mixture flow simulations

In this paper, a coupled Particle-In-Cell (PIC)-Discrete Element Method (DEM) model is developed for numerical simulations of complex fluid–solid mixture flows. The fluid–solid interaction part is solved using the hybrid Eulerian–Lagrangian PIC model, and the solid–solid interaction part is simulated using the Lagrangian DEM model. The PIC model gives the coupled PIC-DEM model both Eulerian efficiency and Lagrangian flexibility, compared to purely Lagrangian methods such as Smoothed Particle Hydrodynamics (SPH). The time step difference between the PIC model and the DEM model is handled using the idea of subcycles. In addition, a straightforward method is proposed for mitigating the issue of unphysical gaps between solids during collision due to the use of the Cartesian cut cell method for fluid–solid interaction. The PIC-DEM model is validated by physical experiments of the collapse of solid cylinder layers with and without water. Following that, the capability of the numerical model is further demonstrated through a more complex problem of solid dumping through fall pipes. The results show great potential of the PIC-DEM model being a useful tool for simulating complex fluid–solid mixture flows

Research on a Model of Extracting Persons\u27 Information Based on Statistic Method and Conceptual Knowledge

PACLIC 21 / Seoul National University, Seoul, Korea / November 1-3, 200

A 3D parallel Particle-In-Cell solver for extreme wave interaction with floating bodies

Floating structures are widely used for vessels, offshore platforms, and recently considered for deep water floating offshore wind system and wave energy devices. However, modelling complex wave interactions with floating structures, particularly under extreme conditions, remains an important challenge. Following the three-dimensional (3D) parallel particle-in-cell (PIC) model developed for simulating wave interaction with fixed bodies, this paper further extends the methodology and develops a new 3D parallel PIC model for applications to floating bodies. The PIC model uses both Lagrangian particles and Eulerian grid to solve the incompressible Navier-Stokes equations, attempting to combine both the Lagrangian flexibility for handling large free-surface deformations and Eulerian efficiency in terms of CPU cost. The wave-structure interaction is resolved via inclusion of a Cartesian cut cell method based two-way strong fluid-solid coupling algorithm that is both stable and efficient. The numerical model is validated against 3D experiments of focused wave interaction with a floating moored buoy. Good agreement between the numerical and experimental results has been achieved for the motion of the buoy and the mooring force. Additionally, the PIC model achieves a CPU efficiency of the same magnitude as that of the state-of-the-art OpenFOAM ® model for an extreme wave-structure interaction scenario

On the hydrodynamic performance of a vertical pile-restrained WEC-type floating breakwater

This paper presents a numerical study on the hydrodynamic performance of a vertical pile-restrained wave energy converter type floating breakwater. The aims are to further understand the characteristics of such integrated system in terms of both wave energy extraction and wave attenuation, and to provide guidance for optimising the shape of the floating breakwater for more energy absorption and less wave transmission at the same time. The numerical model solves the incompressible Navier-Stokes equations for free-surface flows using the particle-in-cell method and incorporates a Cartesian cut cell based strong coupling algorithm for fluid-structure interaction. The numerical model is first validated against an existing experiment, consisting of a rectangular box as the floating breakwater and a power take-off system installed above the breakwater, for the computation of the capture width ratio and wave transmission coefficients. Following that, an optimisation study based on the numerical model is conducted focusing on modifying the shape of the floating breakwater used in the experiment. The results indicate that by changing only the seaward side straight corner of the rectangular box to a small curve corner, the integrated system achieves significantly more wave energy extraction at the cost of only a slight increase in wave transmission

Edge-Mediated Skyrmion Chain and Its Collective Dynamics in a Confined Geometry

The emergence of a topologically nontrivial vortex-like magnetic structure, the magnetic skyrmion, has launched new concepts for memory devices. There, extensive studies have theoretically demonstrated the ability to encode information bits by using a chain of skyrmions in one-dimensional nanostripes. Here, we report the first experimental observation of the skyrmion chain in FeGe nanostripes by using high resolution Lorentz transmission electron microscopy. Under an applied field normal to the nanostripes plane, we observe that the helical ground states with distorted edge spins would evolves into individual skyrmions, which assemble in the form of chain at low field and move collectively into the center of nanostripes at elevated field. Such skyrmion chain survives even as the width of nanostripe is much larger than the single skyrmion size. These discovery demonstrates new way of skyrmion formation through the edge effect, and might, in the long term, shed light on the applications.Comment: 7 pages, 3 figure