Computational Particle Mechanics最新文献

This paper presents a computational study on the flow field, particle trajectory and deposition in a rectangular channel which includes multi-vibrating elastic ribbons mounted on different places of the channel. The diameter of particles varies between 10 μm and 40 μm. Two different places of a vibrating ribbon and four different places of multi-vibrating ribbons are considered. To compare, a fixed ribbon is also considered. Fluid flow equations are solved numerically based on the finite element method. The trajectory of particles was obtained by solving the equation of particle motion that included the inertial, viscous drag and gravity forces. The fluid–structure interaction was considered using an arbitrary Lagrangian–Eulerian method. Detailed analysis of the fluid velocity field and fluid–structure interaction is carried out to investigate the effect of vibrating ribbons on particle deposition. The results were compared with the available experimental and numerical data, and the accuracy of approach was evaluated. Results show that behind the vibrating ribbon, multiple vortices of different sizes are formed, which causes changes in the velocity gradient and flow fluctuations of the upstream and increases the percentage of particle deposition in that area compared to a fixed ribbon. For one ribbon cases, an increase in deposition efficiency is observed when the vibrating ribbon is mounted on the upper wall, and for multi-vibrating ribbon cases, this increase is also observed, but the percentage of deposition is lower than single-ribbon cases. In addition, increasing the diameter of particles and decreasing the Young’s modulus increase the deposition percentage of particles.

This study used an advanced modelling approach capable of capturing the complex behaviour of asphalt concrete to model the modified wheel tracking test using a recent advanced experimental test set-up in accordance with ASTM D8292-20. The modelling approach uses the discrete element method (DEM) to naturally produce the heterogeneous internal structure and governs the behaviour of asphalt concrete at the grain level by an interparticle contact model. The contact model used is capable of characterising the rate and time dependency, viscoelastic-damage, and plastic-damage behaviour of asphalt concrete utilising the coupling of an elastoplastic-damage law with a viscoelastic-damage law. Unlike the conventional wheel tracking tests run in a fixed boundary condition (fully confined), the modified wheel tracking test considers the effect of boundary conditions on the rutting behaviour of asphalt mixes. Through comparisons and verifications with laboratory data of the rutting test at different boundary conditions (fully confined and unconfined), the modelling approach shows its capability of capturing the rutting behaviour of asphalt concrete in the modified wheel tracking test. Micromechanics analysis shows that the third (tertiary) stage of rutting behaviour is due to the weakening of the internal structure of the asphalt samples with contact bond breaks over time, which is found in the unconfined test. Meanwhile, the tertiary stage hardly occurs in the fully confined test once densification leads to contact of the aggregate–aggregate skeleton, forming a rigid structure to resist the load with lateral support from the fixed boundary condition. Finally, a parametric study was also conducted to provide further insight into the current testing set-up, including the effect of the sample size and boundary condition on the rutting behaviour of asphalt concrete.

Proper diagnosis and successful cancer therapy monitoring depend on the early identification of circulating tumour cells (CTCs) in a patient's blood. One of the most promising techniques is the dielectrophoresis (DEP) to separate CTCs from the blood cells. In this paper, to separate distinct multiple CTCs like A549 (lung cancer) CTCs and MDA-MB-231 (breast cancer) CTCs from the normal cells like white blood cell (WBCs) variants and red blood cell (RBCs), a lab-on-a-chip (LOC) device is designed using the positive and negative DEP technique. Two different electrode geometrical shapes, various voltages on electrodes and flow velocity ratios between sample and buffer inlets have been investigated in terms of separation performance in COMSOL Multiphysics 5.4 simulation. The segregation results dependent on finite element method showed that the LOC with trapezoid microcut electrode geometry achieved nearly 100% separation purity and efficiency at 200 kHz driving frequency, 21.6 Vp-p (peak to peak) electrode voltage and 1:2 velocity ratio between sample and buffer inlets.

We anticipate that a design this thorough and methodical will be appropriate to produce DEP-based relevant cell separation biochips.

Understanding the hydraulic fracturing (HF) characteristics of coral reef limestone (CRL) is of great significance for improving the mining efficiency of seabed energy (such as gas and oil) and ensuring the stability of rock masses in marine underground engineering. To investigate the crack evolution mechanism of CRL under hydraulic coupling, numerical simulations of HF on CRL are carried out using particle flow code (PFC). Firstly, a numerical model method based on two-dimensional particle flow code (PFC2D) is proposed to establish the random pore distribution model of CRL, and its effectiveness is verified through indoor experiments. Then, based on the random pore distribution method (RPDM), a numerical model of HF is created, and a calculation formula for breakdown pressure during HF of CRL is established. The breakdown pressure obtained by these two methods is relatively consistent. Finally, the influence mechanism of porosity and confining stress on the hydraulic behavior of CRL is studied. Results indicate that the propagation direction of hydraulic fracture is related to porosity and confining stress. The interactions between pores and hydraulic fractures primarily include penetration, deflection, and obstruction. The presence of pores hinders the transmission of pore pressure, reducing the seepage capacity. With increasing porosity, CRL is more likely to develop macroscopic fractures, leading to fluctuations in water injection pressure. The fluctuations are related to the number of pores involved in crack propagation, pore volume, number of propagation paths, and path length. The breakdown pressure of CRL is affected by the stress on hole walls and confining stress. A higher breakdown pressure on hole walls indicates a greater stability of the surrounding rock under high hydraulic pressures. As for the initiation stress, it is influenced by the confining stress. As the confining stress increases, the breakdown pressure on hole walls increases. For non-uniform confining stress conditions, the breakdown pressure can be determined by the minimum confining stress.

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 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).