Computational Particle Mechanics最新文献

Continuous manufacturing has been increasingly applied in the pharmaceutical industry. The advantages are a more flexible process, decreased costs, and opportunities for better quality control. However, performing experiments is still the way to go when developing a new process but most experiments offer only limited process insight. As part of its ConsiGma® continuous processing lines, GEA has developed a semi-continuous tablet coater with unique design and process mechanics. Simulations enable a deeper understanding of the process mechanics and allow the transition from an empirical process to a mechanistic understanding of the individual process units. We used simulations to improve the understanding of the ConsiGma® tablet coater through a digital multivariate design study. Our simulations demonstrate how the mechanical and material properties influence the tablet bed behavior. We tracked the effects of thermodynamic inputs on the coating quality via the tablet temperature and moisture. These results may be helpful in the future development of coating processes using limited experimental data.

In multiphase SPH method, accurate prediction of oil–water interface is a key, and a major source of failure is due to the nonphysical pressure oscillation. Then in this work, a novel multiphase SPH scheme is designed to solve this problem by integrating several treatments of pressure oscillation together, when the generalized oil–water two-phase flows are simulated. These treatments are: (1) the revised diffusive term which is added in the continuity equation by replacing the original density with the density increment; (2) the corrected density re-initialization during whose implementation different-phase fluid particles must be converted into the imaginary same-phase ones; (3) the particle shifting technique to distribute particles more uniformly. Through the simulation of several generalized oil–water two-phase flow problems as well as comparison with reference solutions, it is validated that our novel SPH scheme is stable, accurate and with less dissipation, and can avoid particle penetration near interface. Finally, a new and more complex generalized oil–water two-phase flow problem is designed and simulated to further demonstrate the above advantages of our SPH scheme.

The material point method (MPM) is a popular and powerful tool for simulating large deformation problems. The hybrid Eulerian–Lagrangian nature of the MPM means that the Lagrangian material points and the Eulerian background mesh are often nonconforming. Once the material and mesh boundaries become misaligned, imposing boundary conditions, such as Neumann boundary conditions (i.e., traction), becomes a challenge. The recently developed virtual stress boundary (VSB) method allows for imposing nonconforming Neumann boundary conditions without explicit knowledge of the boundary position. This is achieved through a problem transformation where the original boundary traction problem is replaced by an equivalent problem featuring a virtual stress field. This equivalent problem results in updated governing equations which are ultimately solved using a combination of particle-wise and cell-wise quadrature. In the current work, a modification to the VSB method is proposed to eliminate the need for cell-wise quadrature. Despite removing cell-wise quadrature, the modified VSB method maintains the accuracy observed in the original approach. Several numerical examples, including 1D and 2D benchmark problems, as well as a 3D demonstration problem, are presented to investigate the accuracy and illustrate the capability of the modified VSB method. Mesh refinement studies are included to show the method’s good convergence behavior.

Sudden expansion pipes are crucial in fluid dynamics for studying flow behavior, turbulence, and pressure distribution in various systems. This study focuses on investigating the behavior of a two-phase flow, specifically a gas–solid turbulent flow, in a sudden expansion. The Eulerian–Eulerian approach is employed to model the flow characteristics. The Eulerian–Eulerian approach treats both phases (gas and solid) as separate continua, and their interactions are described using conservation equations for mass, momentum, and energy. The study aims to understand the complex phenomena occurring in the flow, such as particle dispersion, turbulence modulation, and pressure drop. The governing equations are solved using house developed code called FORTRAN, a widely used programming language in scientific and engineering simulations. The results of this study will provide valuable insights into the behavior of gas–solid two-phase flows in sudden expansions, which have important applications in various industries, including chemical engineering, energy systems, and environmental engineering. A parametric study of the impact of particles diameters (20, 120, 220, 500 µm), the solid volume loading ratios ((0.005, 0.008, 0.01)) and area ratios (2.25, 5.76, 9) effect of sudden expansion on the streamlines, local skin friction, pressure, velocity, turbulent kinetic energy, and separation zone.

Treating ballast and subgrade soil as an integrated unit for sampling and loading has proven to be an effective method for investigating the interaction between ballast and subgrade soil. Given that direct testing of specimens containing large ballast is constrained by the capabilities of standard laboratory equipment, adopting a model material of smaller size is recommended. Parallel gradation method is widely used for this purpose. This study performed an evaluation of parallel gradation method based on the response of ballast penetration into subgrade soil. Discrete element models were developed to simulate the penetration of crushed ballast, featuring three different parallel gradations, into subgrade soil. On this basis, dynamic triaxial simulations were conducted on these models. By comparing the macroscopic and mesoscopic mechanical characteristics at different scaling ratio, the applicability of the parallel gradation method for assessing ballast penetration into subgrade soil was evaluated. At the macroscopic scale, the scaling ratio of crushed ballast significantly influences the axial, volumetric, and lateral deformations observed during penetration into subgrade soil. Specifically, a smaller average grain size of ballast correlates with reduced deformations in these specimens. The penetration of crushed ballast into subgrade soil significantly increases the porosity of subgrade soil, particularly at the interface between ballast and subgrade. This increase in porosity is more pronounced with larger average grain sizes of ballast. At the mesoscopic scale, larger average grain sizes of ballast lead to more localized high contact forces and more significant stress concentrations. The parallel gradation method substantially affects the mechanical properties of ballast penetration into subgrade soil, at both macroscopic and mesoscopic scales. Therefore, a cautious approach is necessary when relying on this method for precise assessments.

Rockslide is a hot topic and universal phenomenon in the mountainous regions prone to geological hazards, which may pose substantial threats to property. The discrete element method (DEM) has been widely used to simulate the movement process of rockslide and avalanche. However, the rockslide involving jointed rock mass needs more adequate study to evaluate the safety implications effectively. In this paper, a series of DEM tests are conducted to study the movement and fragmentation of blocks with varying structure. The results show that at sliding angle of 45°, horizontal velocity reduces more slowly than vertical velocity because the particles move in a forward direction after impacting the bottom wall. The existence of a baffle structure limits sliding particle movement effectively and enhances the arch effect through the distribution of contact force chains. The number of joints, slope angle and sliding distance have considerable impact on bond breaking percentages and the displacement of the rock mass center. All bond break percentages are close to 90%, and number of joints and slope angle have little impact on the displacement of the rock mass center. This study can guide landslide disaster prevention.

Virtual crime scene investigation using numerical models has the potential to assist in the forensic investigation of firearm-related fatalities, where ethical concerns and expensive resources limit the scope of physical experiments to comprehend the post-impact biomechanics comprehensively. The human cranial numerical model developed in this study incorporates three main components (skin, skull, and brain) with dynamic biomaterial properties. The virtual model provides valuable insights into the post-impact biomechanics of cranial ballistic injuries, particularly in high-speed events beyond conventional investigative capabilities, including the velocity of ejected blood backspatter, cavitation collapsing, and pressure waves. The validation of the numerical model, both quantitatively and qualitatively, demonstrates its ability to replicate similar bone fractures, entrance wound shapes, and backward skin ballooning observed in physical experiments of the human cranial geometry. The model also yields similar temporary cavity sizes, wound sizes, and blood backspatter time against the physical cranial model, aiding in bloodstain pattern analysis. Additionally, the numerical model enables exploration of ballistic factors that vary in each crime scene environment and influence cranial injuries, such as projectile type, velocity, impact location, and impact angle. These established injury patterns contribute to crime scene reconstruction by providing essential information on projectile trajectory, discharge distance, and firearm type, assisting in the resolution of court cases. In conclusion, the developed human cranial geometry in this study offers a reliable tool for investigating firearm-related cranial injuries, serving as a statistical reference in forensic science. Virtual crime scene investigationsusing these modelshave the potential to enhance the accuracy and efficiency of forensic analyses.