Computational Particle Mechanics最新文献

In this paper, an accurate meshless method for solving time-fractional wave equation (TFWE) based on KDF-SPH approximation is proposed. In this method, finite difference method is used to discretize the time-fractional derivative defined in the Caputo sense. The spatial discretization is achieved using KDF-SPH meshless method. At the same time, the kernel approximation and particle approximation expressions are given. In order to prove the effectiveness and order of numerical convergence of the proposed method, a number of 1D and 2D initial boundary value problems are numerically simulated in regular and irregular domains, and the meshless method is compared with the existing methods. Numerical results show the effectiveness and accuracy of the proposed method, and the second-order accuracy is achieved in space in the regular calculation area.

Several gradations of concrete with fractal dimension D = 2.0–2.9 (i.e., 2.0, 2.2, 2.4 2.6, 2.7, 2.8, 2.9) were designed based on particle size-mass distribution fractal model. The random polyhedral aggregate model was generated and then imported particle flow code, the discrete element method (DEM), to establish a multi-phase model considering mortar, aggregate, and interfacial transition zone (ITZ). On this basis, the relationship between fractal dimension D and macro-mechanical properties and microstructure of concrete was discussed, and the grading evaluation index was proposed based on fractal dimension D. The results show that the number of large-size aggregates decreases with increase in the fractal dimension, the compressive strength of concrete increases and reaches the maximum when the fractal dimension D = 2.7. Meanwhile, the fractal dimension affects the failure mode, as fractal dimension D increases, the total microcracks gradually increase, among which the ITZ microcracks increase mainly. Compared with the uncertainty of the non-uniformity coefficient and curvature coefficient, the fractal dimension can more accurately describe the aggregate grading characteristics. In addition, appropriate adjustments should be made to determine the range of fractal dimensions considering the differences between the aggregate filling.

This paper aims to analyse electrical conduction in partially sintered porous materials using an original resistor network model within discrete element framework. The model is based on sintering geometry, where two particles are connected via neck. Particle-to-particle conductance depends on neck size in sintered materials. Therefore, accurate evaluation of neck size is essential to determine conductance. The neck size was determined using volume preservation criterion. Additionally, grain boundary correction factor was introduced to compensate for any non-physical overlaps between particles, particularly at higher densification. Furthermore, grain boundary resistance was added to account for the porosity within necks. For numerical analysis, the DEM sample was generated using real particle size distribution, ensuring a heterogeneous and realistic microstructure characterized by a maximum-to-minimum particle diameter ratio of 15. The DEM sample was subjected to hot press simulation to obtain geometries with different porosity levels. These representative geometries were used to simulate current flow and determine effective electrical conductivity as a function of porosity. The discrete element model (DEM) was validated using experimentally measured electrical conductivities of porous NiAl samples manufactured using spark plasma sintering (SPS). The numerical results were in close agreement with the experimental results, hence proving the accuracy of the model. The model can be used for microscopic analysis and can also be coupled with sintering models to evaluate effective properties during the sintering process.

We consider a liquid bridge between identical spheres and present approximate expressions for the capillary force and the exposed surface area of the liquid bridge as functions of the liquid bridge’s total volume and the sphere separation distance. The radius of the spheres and the solid–liquid contact angle are parameters that enter the expressions. These expressions are needed for efficient numerical simulations of drying suspensions and other systems involving liquid bridges whose volume or shape vary in time.

Investigating and analyzing circulating tumor cells (CTCs) have shown to be an invaluable tool for early cancer detection and diagnosis. Microfluidic devices, which are inexpensive and simple to use, have recently gained a lot of attention for the enumeration and separation of CTCs. In this research, a novel sheathless double-loop spiral-based lab-on-a-chip is proposed dependent upon the functionality of inertial focusing for separating multiple CTCs such as MCF-7 (breast cancer CTCs) and A549 (lung cancer CTCs) distinctly from the normal cells like WBCs (white blood cells) and RBCs (red blood cells). The chip is designed and examined in numerical simulation using COMSOL Multiphysics 5.4 tool at various average flow velocities and Reynolds numbers (Re). In this study, the separation purities and recoveries of (sim ) 100% is gained by the chip at the Re values ranges from 71.75 ({text{to}}) 76.87 (flowrate of 87.8(-)94.1 ml/h), which indicates the high capability of separating multiple CTCs distinctly with high throughput.

A modified version of a nonlinear viscoelastic damping model is presented to better represent overall spherical particle response using the discrete element method (DEM) to simulate gravity-driven mixing of binary particles into a confined box. Nonlinear springs are used in the normal and tangential directions to simulate the contact forces, and an additional nonlinear annular spring is employed at the contact points to account for rolling friction. A viscous damping term related to the relative motion between contacting particles is applied to represent energy dissipation, and an alternative condition for checking the end of a collision is applied. The new model is shown to successfully recover the tangential force behavior in stick and sliding regions without having to introduce more complicated behavior. Results are in excellent agreement with existing benchmark tests, and the model is applied to evaluating several different mixing schemes using fixed geometric particle flow disruptors with sometimes surprising results.