Computational Particle Mechanics最新文献

In this study, three-dimensional laser scanning technology is applied to obtain real geometric data of aggregate particles in cemented materials, and a characterization method of surface roughness of aggregate is proposed to quantify the surface roughness of aggregate. A series of three-dimensional direct shear tests are conducted using particle flow code. The shear mechanical properties of cemented materials with different cementation degrees and different surface roughness levels of aggregate particles are investigated through the direct shear tests. The results show that the roughness level of aggregates and the cementation degree both affect the mechanical properties of cemented materials. As the degree of cementation increases, both of the internal friction angle and cohesion increase. As the degree of roughness increases, the internal friction angle increases while the cohesion decreases. The surface roughness of aggregate is in linear relationship with the internal friction angle and in nonlinear decreasing relationship with the cohesion.

In aerospace and automotive industries, the control of thermal flows and particulate matter is crucial for the efficient operation of engine cooling systems and optimizing the aerodynamics of vehicles. Understanding the dynamics of natural phenomena such as the movement of volcanic ash, dust storms, and other astrophysical and geophysical flows influenced by thermal and magnetic forces is essential. Within this framework, the primary objective of our study is to develop a model and simulate the heat-driven movement of a solid dust particulate-embedded fluid influenced by thermal emission and magnetic forces in a slanted channel. Our approach utilizes the Casson fluid model to represent the dusty fluid’s characteristics. The model takes into account emerging factors like buoyancy force, radiant heat flux, velocity slip condition, and periodic thermal boundary conditions. To mathematically describe the time-dependent flow, partial differential equations are employed, and compact-form solutions are derived. A series of graphs and tables are constructed to demonstrate the aftermath of various contextual parameters on flow profiles and related quantities. These visual aids effectively portray the changes in the flow dynamics under different conditions. The research reveals that in the fluid phase (FP), the velocity and thermal fields generally display higher values, whereas in the dust phase (DP), these values are lower within the channel. As particles’ concentration parameter upsurges, the thermal curve declines, irrespective of whether it is FP or DP. Additionally, the shear stresses at the channel walls intensify with increased particle relaxation time. Notably, pronounced periodic temperature fluctuations at the right wall significantly influence the heat transfer rates at both channel walls. This research can aid in designing more effective air filtration systems, refining vehicle design for improved aerodynamics, and managing particulate pollutants in industrial settings.

In this research, the breakage behavior of rock pillars under the uniaxial compressive strength test is investigated using both experimental and three-dimensional discrete element methods. Gypsum samples with rectangular and hourglass hexagonal shapes are constructed to simulate underground mine pillars. Within the samples, various settings of created holes in different angles, numbers, and shape patterns are considered to design a total of 20 configurations for the failure test. Twelve layouts included horizontal rows of 5 holes (1, 2, or 3 rows) at different angles (0°, 30°, 60°, and 90°). The hole patterns in the other 8 arrangements involved some usual geometric shapes including vertical ellipse, vertical rectangle, triangle, horizontal ellipse, horizontal rectangle, diamond, trapezoid, and square. For the experimental tests, 60 specimens are prepared (3 samples for each configuration to increase reliability). For the PFC3D simulations, 20 models with similar setups are prepared to replicate the experiments. The loading rate was set to 0.016 m/s. Our results show that the hole parameters, i.e., angles, numbers, and shape configurations, are the key factors in the failure process. Our analysis helps reveal a correlation between the breakage pattern, the breakage mechanism of discontinuities, and the maximum applied force of the specimens. Increasing the hole angles and numbers add to the total crack number (TCN). The minimum load-carrying capacity of the samples is recorded for the sample with 15 holes at 30° and 60° angles.

In this study, a novel particle shifting scheme for the moving particle method simulating free surface flow is developed. The overall method is based on the framework of least square moving particle semi-implicit (LSMPS) method, enabling accurate and stable treatment of wall boundary without configuration of dummy or virtual wall particles. To avoid volume expansion, a volume-conservation particle shifting (VCPS) model is developed. An additional term considering the variation of particle numerical density is incorporated into the VCPS model to avoid volume expansion. Several numerical simulations are calculated to validate the effectiveness of the VCPS. It is demonstrated that LSMPS incorporating with VCPS shows satisfactory accuracy and superior capability to conserve volume.

The microstructure of the electrode and its mechanical properties are important factors affecting the performance of lithium batteries. Calendering is one of the most important aspects that affect the microstructure and mechanical response of lithium battery electrodes. Discrete element method was employed to establish a lithium battery electrode model that considered the real particle shape and size distribution. Subsequently, calendering simulations were conducted to reveal the microstructure evolution and mechanical properties of the electrode in the deformation zone. The results show that the electrode density and porosity in the calendering deformation zone change sharply at first and then slow down, and the appropriate increase of the roller diameter is helpful to alleviate this phenomenon. Calendering will cause the pore sizes in the electrode to become smaller, and this process reduces the floating range of the pore sizes. The stress change of the electrode during the calendering process mainly occurs in the normal direction (z-direction), but there is also a small stress change in the length direction (x-direction).

In mineral processing, ore grinding is an energy-intensive process. Tumbling mills used in grinding processes can be accounted for as rotating drums with liners. As part of an effort to evaluate ways of reducing energy consumption in such systems, therefore, particulate flows in rotating drums are studied in this work. More specifically, using a new DEM tool, which is one of the modules of a larger in-house computational package called CFLOWSS, particulate flows in rotating drums are qualitatively and quantitatively analyzed. The results from such analyses are compared with experimental ones and other numerical results obtained using a commercial DEM software. In qualitative terms, the CFLOWSS results show a relatively good agreement with experimental photographs previously taken in a laboratory. In quantitative terms, in turn, the CFLOWSS predictions show a strong correspondence with those ones made by the commercial software. For instance, the relative discrepancies of the boxplots’ medians associated with the number of contacts, power, and forces predicted by both (in-house and commercial) tools present values smaller than 8%. At a 60 RPM drum rotation velocity, indeed, the number of contacts related discrepancies reach values as low as 0.8%. Some of the contributions of this work involve (i) the development of a new DEM tool capable of realistically describing particulate flows in rotating drums, and (ii) the use of statistical treatments to quantitatively analyze DEM results. This last aspect is important because this sort of assessments provides an improved way to analyze the behavior of particulate flows.

The deep-buried rock is subjected to true triaxial stress states and is affected by repeated disturbance loads. The discrete element method was employed to investigate the mechanical behavior and fracture mechanism of marble under true triaxial cyclic loading and unloading. The particle-based marble model with the calibrated microparameters was established based on true triaxial compression. The true triaxial cyclic loading and unloading simulations with different stress states were conducted. The increase in intermediate principal stress results in significant deformation anisotropy. The brittle–ductile transformation characteristics are presented with the increase in minimum principal stress. The crack damage stress initially increases and subsequently decreases with the increase of equivalent plastic strain under different stress states. The plastic strain increments ratios exhibit prominent nonlinear variation during the progressive failure. The rock strength presents the asymmetric distribution by the effect of intermediate principal stress, and the minimum principal stress has an enhancing effect on strength. With the increase in intermediate principal stress or the decrease in minimum principal stress, that is, the effect of high differential stress, the failure plane changes from inclined to parallel to the direction of maximum principal stress. The microcrack numbers present the S-shaped increasing trend during the progressive failure. The increasing number of microcracks parallel to the direction of intermediate principal stress and the anisotropy of microcrack tendency are subjected to high differential stress.

The collapse of bubbles in hydraulic machinery has emerged as a prominent area of research. To grasp the interplay between bubbles, a model of double-bubbles is built. The bubble morphology, total pressure (P), and the center of mass displacement (L_com) are taken as research objects, and the influence temperature (T), and bubble radius (R), bubble distance (L) on bubble collapse is summarized. Results show that the distance between the bubbles is smaller, the total collapse time is longer. However, L_com increases when the distance is increased or decreased to some extent. Moreover, in the case of the double-bubbles model with r₁ = 10 Å, as the bubbles (r₂ = 7.5, 10, 12.5 Å) collapse, the released pressure gradually increases, then decrease, and the release pressure of the double-bubbles model (r₁ = 10 Å, r₂ = 12.5 Å) is 1.08 times that of the model (r₁ = 10 Å, r₂ = 15 Å). Based on the differential pressure parameters (∆P₁ and ∆P₂), the significance order of temperature (T), bubble distance (L), and bubble radius (r) is L ≈ r > T. The aim of the paper is to provide technical guidance and a theoretical basis for industrial applications of techniques by enhancing the theory of cavitation.

Material Point Method is used to study the impact deformation of elastic-perfectly plastic spherical particles. A wide range of material properties, i.e. density, Young’s modulus and yield strength, are considered. The method is particularly suitable for simulating extensive deformation. The focus of the analysis is on linking the coefficient of restitution and the percentage of the incident kinetic energy dissipated by plastic deformation, W_p/W_i × 100, to the material properties and impact conditions. Dimensionless groups which unify the data for the full range of material properties have been identified for this purpose. The results show that when the particle deforms extensively, W_p/W_i × 100 and the equivalent plastic strain, are only dependent on the particle yield strength and the incident kinetic energy, as intuitively expected. On the other hand, when the deformation is small, Young’s modulus of the particle also affects both W_p/W_i × 100 and the equivalent plastic strain. Moreover, coefficient of restitution is insensitive to Young’s modulus of the material. Dimensionless correlations are then suggested for prediction of the coefficient of restitution, the equivalent plastic strain and W_p/W_i × 100. Finally, it is shown that the extent to which the particle flattens due to impact can be predicted using its yield strength and initial kinetic energy.