Particle Method Research Articles

Development of PIND system based on resonant sensors and research on material identification methods for redundant particles

Abstract Aiming at the problems of the existing particle impact noise detection (PIND) system, such as low detection accuracy, high rate of misjudgment and missed judgment, and the inability to judge the material of internal redundant particles in real time, a method for automatic detection and material identification of redundant particles based on neural network recognition is proposed, and an automatic detection system for redundant particles of sealed electronic devices is developed. The system is equipped with multi-channel piezoelectric resonant sensors, which convert the redundant particle impact noise signal into a voltage signal, and then transmit the signal to the host using a high-speed data acquisition system. The upper computer uses a short-term energy threshold detection method to extract signal pulses; Then, a variety of time and frequency domain features are extracted and combined with wavelet domain features; Finally, by training the multi output neural network prediction model, it can automatically judge whether there are redundant particles in the tested parts, and automatically give the material information of the redundant particles. Experiments show that the accuracy of the system for material recognition of redundant particles with a mass greater than 0.1 mg can reach 88.6%.

Numerical simulation of interior ballistics two-phase flow in modular charge based on the particle element method

The full combustibility and strong discontinuity characteristics of module charge result in significant differences from conventional mode, making it challenging for traditional two-fluid methods to effectively reveal its particle dispersion mechanism. In this study, the particle element method for module charge were developed and applied for modeling the interior ballistics to overcome above drawback. Firstly, based on the characteristics of module charge and particle aggregation, criteria for dividing particle elements and methods for motion calculation are proposed. Next, particle element solver and CFD solver are constructed and mutually coupled for solution. Finally, validation is conducted under the condition of three modules charging. The computational results show that the particle element method can effectively predict the pressure and velocity inside the chamber, consistent with experimental results, the pressure error is 5.55 % and the velocity error is 0.79 %. The particle element method reproduces the combustion process with variable particle mass, accurately presenting the distribution of the flow field and temperature. Moreover, it fundamentally explains that pressure fluctuations occur due to the presence of free space and changes in the flow field caused by the movement of the propellant bed. The particle element method can provide scientific research methods and technical support for the development of module charge technology.

A computational study on buckling strength of pressurised submarine pressure hull structures under combined static load and asymmetric impact load

Through the reconstructed kernel particle method (RKPM), the dynamic buckling characteristics of submarine pressure hull under hydrostatic pressure and impact load is investigated in this study. First, a large deformation buckling calculation model for stiffened shell structures was established using RKPM and elastic–plastic constitutive models. To study the influence of load asymmetry on the buckling strength of the structure and provide fundamental technical support for submarine structural design, the dynamic buckling phenomenon of the structure was studied under three conditions: hydrostatic pressure acting alone, hydrostatic pressure and impact load acting simultaneously, and hydrostatic pressure and uniformly distributed impact load acting simultaneously. The starting time of buckling was used as the criterion for determining the critical load of dynamic buckling. The results indicate that under the combined action of static and dynamic loads, asymmetric dynamic loads can seriously affect the buckling strength of the structure.

Gaussian smoothed particle hydrodynamics: A high-order meshfree particle method

Smoothed particle hydrodynamics (SPH) has attracted significant attention in recent decades, and exhibits special advantages in modeling complex flows with multiphysics processes and complex phenomena. Its accuracy depends heavily on the distribution of particles, and will generally be lower if the particles are distributed non-uniformly. A high-order SPH scheme is proposed in the present work for simulating both compressible and incompressible flows. It uses a Gaussian quadrature rule to perform the particle approximation of SPH by introducing Gaussian nodes. Unfortunately, the Gaussian nodes hardly overlap with SPH particles due to the Lagrangian feature, and thus we use a high-order interpolation method to obtain the corresponding physical quantities at the Gaussian nodes. The accuracy and robustness of the proposed Gaussian SPH are demonstrated by several numerical tests, including the Sod problem, Poiseuille flow, Couette flow, cavity flow, Taylor–Green vortex and dam break flow, and a convergence analysis is also conducted to evaluate the effects of particle resolution and distribution for reconstructing a given function. The simulation results for each test case are in good agreements with the available analytical, experimental or numerical results, showing that the proposed Gaussian SPH method is accurate and reliable but expensive for simulating compressible and incompressible flow problems.

An improved stochastic weighted particle method for boundary driven flows

The stochastic weighted particle method (SWPM) is a generalization of the Direct Simulation Monte Carlo (DSMC) method where particle weights are variable and dynamic. SWPM is backed by a strong theoretical foundation but has not been critically evaluated for problems of practical interest. A thorough assessment of SWPM for boundary-driven flows reveals significant numerical artifacts near the boundary, notably a diverging heat flux. To correct the boundary heat flux, two modifications to SWPM are proposed: separated grouping and a spatially-dependent weight transfer function. To gauge the relative efficiency of SWPM in comparison to DSMC, a high-Mach-number wheel flow which forms a strong density gradient is also simulated.

Image-based modeling of coupled electro-chemo-mechanical behavior of Li-ion battery cathode using an interface-modified reproducing kernel particle method

Image-based modeling of coupled electro-chemo-mechanical behavior of Li-ion battery cathode using an interface-modified reproducing kernel particle method

Updated measurement method for transparent exopolymer particles (TEPs) and their precursors with insights into efficient monitoring

Transparent exopolymer particles (TEPs) and their precursors play a critical role in various environmental processes, including contaminant transport and membrane fouling. This study presents an improved Alcian blue (AB) staining-based TEP measurement method and investigates spectroscopic proxies to enhance analysis convenience and reproducibility. The proposed method employs deionized (DI) water and sonication to extract particulate TEPs (TEP0.4μm) and particulate TEPs and their precursors (TEP10kDa), thus eliminating the need for concentrated sulfuric acid and simplifying the procedure with an integrated standard curve. This AB-DI method had a low detection limit of 5 μg Xeq/L for a 1 L sample volume, allowing precise measurements to be made across a broad concentration range. When used in wastewater treatment and microfiltration membrane filtrates, the AB-DI method provided insights into the removal mechanisms of TEPs and their precursors. This study also identified effective spectroscopic proxies by correlating TEP concentrations with optical properties, achieving remarkable estimation accuracy using the UV254 absorbance of TEP-extracted solutions. The UV254 and fluorescence intensities of the protein-like peaks in raw water samples demonstrated significant potential as proxies for TEPs and their precursors. The proposed AB-DI method represents a viable approach for the real-time TEP monitoring for desalination and water reuse processes.

Multi-layered solid element for seismic analysis of rubber bearings considering stress continuity based on finite particle method

Rubber bearings are crucial components in seismic isolation systems to mitigate the damaging effects of earthquakes on structures. Rubber bearings generally consist of alternate layers of steel and rubber bonded together. Simplified two-point spring models omit this layered construction and have limitations in adaptability and programmability, while refined multiple solid models lead to substantial computational costs. This study presents an effective and efficient approach to simulate rubber bearings by using multi-layered solid element based on the finite particle method (FPM). The traditional “Zigzag” shape function is extended into the 3D situation to reflect the serrated deformation within the layered construction. Based on the simplified assumption of stress continuity, an iterative approach is presented for the deformation gradient to achieve the force continuity between layers in dynamic nonlinear scenarios. The multi-layered solid models for both natural rubber bearings (NRBs) and lead rubber bearings (LRBs) are proposed based on this element. The errors of the hysteresis curves of rubber bearings are below 3.1 % between the numerical results obtained by using the multi-layered solid model and the experimental results. The computational speedup ratio of the proposed multi-layered solid model is verified to be 19 relative to the refined multiple solid model. The proposed method is applied to a base-isolated frame structure to demonstrate its effectiveness in structural seismic analysis.

Study on the formation and dewatering process of the surface filter cake of geotextile on the lateral boundary of geotextile tubes under constant flow grouting

In this article, physical model test and numerical simulation are used to study the formation of filter cake and the filtration performance of the geotextile on the lateral boundary of the ultra-fine tailings grouting geotextile tubes from macro and micro levels. At the macro level, the effects of different grouting flow rates and tailings slurry mass concentrations on the surface filter cake formation and the dehydration performance of geotextile on the lateral boundary of the geotextile tubes were analyzed. At the micro level, the use of CFD-DEM method for fluid and particle of two-way coupling numerical simulation research, lateral drainage boundary of superfine tailings in tubes filter cake forming process is analyzed. The research shows that the increase of grouting flow rates and tailings slurry mass concentrations will make the thickness of filter cake great and the structure more compact, which will lead to more serious silting of the surface layer of geotextile and greatly reduce the dehydration performance; The numerical simulation results regularity is consistent with the results regularity of physical model test on the formation of filter cake on geotextile surface of geotextile tubes: the larger the slurry inlet speed and particles concentrations, the more complete the formation of filter cake on geotextile surface, the denser the cake structure, and the less tailings loss. By studying the effects of grouting flow rates and slurry mass concentrations on the surface filter cake formation and tubes dehydration, this article aims to find suitable slurry filling construction conditions and explore the main influencing factors caused by dehydration and consolidation of ultra-fine tailings grouting geotextile tubes, so as to provide some help for the subsequent flocculating of ultra-fine tailings to solve the problem of surface drying and internal wetting of geotextile tubes.

A finite pointset method for Kuramoto–Sivashinsky equation based on mixed formulation

In this paper, a second‐order splitting method is applied to the Kuramoto–Sivashinsky equation, and then a finite Pointset method (FPM) is employed to solve the resulting coupled system. FPM is a meshfree particle method which is a local iterative procedure based on the weighted least square approximation. The numerical example confirms that the FPM is effective and accurate for this kind of problem.

HPC software for modelling field electron emission

The aim of this work is modeling processes of field electron emission in strong electromagnetic fields. This problem is relevant for many technical and medical applications. At present time, electrical devices that combine a large value of field, a powerful relativistic effect and an ultra-short time interval of action are in demand. They find their application in the treatment of the surfaces with inorganic, organic and mixed structures. Modeling of such devices encounters certain difficulties due to the complexity of the mathematical description of the emission processes. In this paper, an approach using the method of large smoothed particles in combination with grid calculation of fields based on Maxwell's equations is proposed. The study was carried out within the framework of the problem of calculating the field emission of electrons from the surface of axisymmetric metal cathodes on Cartesian and unstructured curved meshes. To implement the approach, a complex mathematical model, a parallel numerical algorithm and its software realization have been developed. The elaborated software is focused on the use of multiprocessor computing systems with a central architecture. Test calculations confirmed the correctness of the proposed approach and the high efficiency of its software implementation.

Embedment of WENO-Z reconstruction in Lagrangian WLS scheme implemented on GPU for strongly-compressible multi-phase flows

It is a notoriously challenge problem for Lagrangian particle methods to solve compressible flows with strong discontinuities and large volume variations. To overcome the problems of numerical oscillations, an accurate and stable Lagrangian Weighted-Least-Square (LWLS) method embedded with WENO-Z scheme (LWLS-WENO-Z) is proposed. To further enhance the numerical accuracy and stability, the particle shifting technique, the multi-level local-refinement technique, and the interface repulsive force are appropriately employed in the numerical scheme. Moreover, the smooth and stable coupled particle method between the LWLS and Roe's Riemann solver (LWLS-RR) is considered for the comparisons, further demonstrating the merit of the proposed LWLS-WENO-Z scheme. To reduce the simulation time, parallel computing with a CUDA-based program for the proposed scheme is implemented on a single GPU. In the numerical experiments, several 1D/2D benchmarks are solved to test the accuracy of the proposed method. Particularly, the challenge 2D underwater explosion and the cavitation bubble collapse and jetting are numerically investigated. Compared to other reference solutions, the present coupled particle method demonstrates robustness and superior accuracy in simulating these strongly-compressible multi-phase flows.

THE EFFECT OF PRECURSOR CONCENTRATION, pH OF THE SOLUTION AND CARBONATION DURATION ON CACO3 PARTICLE SIZE VIA CARBONATION METHOD

Background. There are multiple techniques for generating CaCO3, one of which is the carbonation method. Currently, the particle size of CaCO3 is primarily determined by the combined influence of various variables. Objective. This study investigates the effect of precursor concentrations, pH of the solution, and carbonation duration on the size of CaCO3 particles Methods. The type of research in this study is experimental laboratory with a descriptive presentation of data. This study is divided into two stages: first, synthesis of CaCO3 with different concentration of precursors and carbonation duration. Second, it used different pH value of the solution and carbonation duration. The particle size of CaCO3 were characterized using the Particle Size Analyzer (PSA) (Horiba Scientific SZ-100 Nanopartica). Result. The result show the smallest CaCO3 at first stage, 548 nm, obtained at concentration of 0.75 M with carbonation duration of 30 minutes. The largest CaCO3-size, 6194 nm, is seen at a 0.5 M concentration with a carbonation duration of 10 minutes. The second stage show the smallest particle size, 1165 nm, obtained at a pH value of 8 with a carbonation duration of 60 minutes. Meanwhile, the largest size, 5621 nm, is obtaining at a pH value of 9 with a carbonation duration of 90 minutes Conclusion. The concentration of precursors and the duration of carbonation have no effect on the size of CaCO3 particles, however the pH value of the solution may affect the particle size of CaCO3. It is directly proportional to the pH value of the solution

Research on multi-velocity measurement method of solid particles based on interdigital electrostatic sensor

Abstract In gas-solid two-phase flow, the velocities of solid particles will show different distributions as the flow pattern changes, and it is a challenging task to achieve the measurement of different velocity parameters in the flow field. To obtain the velocity information of solid particles in the flow field, a novel method to achieve multi-velocity measurement of solid particles is proposed by using the spatial filtering characteristics of interdigital electrostatic sensor with variational mode decomposition (VMD). Firstly, a three-dimensional model of the interdigital electrostatic sensor is established using COMSOL simulation software. Based on its spatial dynamic sensitivity, a theoretical analysis of its spatial filtering characteristics is conducted to obtain a mathematical relationship for velocity measurement. Subsequently, the VMD decomposition method is applied to an experiment involving charged wires, with the experimental results verifying the effectiveness of VMD in achieving multi-scale decomposition of electrostatic signals. Finally, the proposed measurement method is validated on a gravity feeding device and a pneumatic conveying system. The experimental results demonstrate that the method exhibits good feasibility.

Regularized Stein Variational Gradient Flow

AbstractThe stein variational gradient descent (SVGD) algorithm is a deterministic particle method for sampling. However, a mean-field analysis reveals that the gradient flow corresponding to the SVGD algorithm (i.e., the Stein Variational Gradient Flow) only provides a constant-order approximation to the Wasserstein gradient flow corresponding to the KL-divergence minimization. In this work, we propose the Regularized Stein Variational Gradient Flow, which interpolates between the Stein Variational Gradient Flow and the Wasserstein gradient flow. We establish various theoretical properties of the Regularized Stein Variational Gradient Flow (and its time-discretization) including convergence to equilibrium, existence and uniqueness of weak solutions, and stability of the solutions. We provide preliminary numerical evidence of the improved performance offered by the regularization.

Noise radiation from a partially opened and elevated tunnel-tube

Road or railway tunnels are considered in noise prediction programs generally by neglecting any emission from the tunnel structure between the openings and replacing each tunnel mouth by additional sources simulating the sound radiated from inside to outside through these openings. The sound pressure level inside the tunnel can be derived from the analog model of a room formed by a slice cut out of the extended tunnel with two perfect reflecting planes perpendicular to the tunnel axis. The paper presents a methodology for the case of an elevated tunnel tube with an upper ventilation gap running over the entire length of the tunnel to calculate the sound pressure levels in the surrounding area more approximately using engineering models like ISO 9613-2 or others and more detailed using a particle method developed to account for complete 3-dimensional propagation problems.

Enhanced schemes for resolution of the continuity equation in projection-based SPH

To the best knowledge of the authors, the numerical resolution of the continuity equation, i.e., the simultaneous achievement of accurate and physically consistent velocity divergence and density fields, has not been investigated in the context of projection-based particle methods. In this study, based on the Velocity-divergence Error Mitigating (VEM)/Volume Conservation Shifting (VCS) schemes developed for the WCSPH method, which improve the numerical resolution of the continuity equation, VEM/VCS schemes are proposed for projection-based particle methods. Furthermore, two other novel schemes are introduced. First, a Dynamic VEM (DVEM) scheme is proposed, where VEM is dynamically activated only when the velocity divergence instantaneously diverge from the reference solution at individual particles. The second scheme is referred to as Enhanced VCS by reference density (EVCS), where precise imposition of dynamic free surface boundary condition is considered. Several benchmark tests with different features have been conducted, and it is shown that the proposed schemes enhance the numerical resolution of the continuity equation for incompressible flows, i.e., the divergence free velocity and the constant density conditions. Application of DVEM and EVCS has provided enhanced resolution of the continuity equation along with clear reductions in the numerical energy dissipation associated with the approximated additional numerical terms.

Gradient-Based Monte Carlo Methods for Relaxation Approximations of Hyperbolic Conservation Laws

Particle methods based on evolving the spatial derivatives of the solution were originally introduced to simulate reaction-diffusion processes, inspired by vortex methods for the Navier–Stokes equations. Such methods, referred to as gradient random walk methods, were extensively studied in the ’90s and have several interesting features, such as being grid-free, automatically adapting to the solution by concentrating elements where the gradient is large, and significantly reducing the variance of the standard random walk approach. In this work, we revive these ideas by showing how to generalize the approach to a larger class of partial differential equations, including hyperbolic systems of conservation laws. To achieve this goal, we first extend the classical Monte Carlo method to relaxation approximation of systems of conservation laws, and subsequently consider a novel particle dynamics based on the spatial derivatives of the solution. The methodology, combined with asymptotic-preserving splitting discretization, yields a way to construct a new class of gradient-based Monte Carlo methods for hyperbolic systems of conservation laws. Several results in one spatial dimension for scalar equations and systems of conservation laws show that the new methods are very promising and yield remarkable improvements compared to standard Monte Carlo approaches, either in terms of variance reduction as well as in describing the shock structure.

Fluid–Structure Interaction Analysis of Manta-Bots with Self-Induced Vertical Undulations during Fin-Based Locomotion

Driven by the demands of ocean exploration, an increasing number of manta ray-inspired robots have been designed and manufactured, primarily utilizing flexible skeletons combined with motor-driven mechanisms. However, the mechanical analysis of these designs remains underdeveloped, often relying on simplistic imitation of biological prototypes and typically neglecting the vertical motion induced by pectoral fin flapping. This paper presents a fluid–structure interaction analysis framework that couples rigid body motion with elastic deformation using flexible multibody dynamics and the vortex particle method. An implicit iterative algorithm with Aitken relaxation is employed to address added-mass instability, and the framework has been validated against experimental data. An analysis of a representative manta-bot model shows that self-induced vertical undulations reduce the thrust coefficient by approximately 40% compared to fixed vertical degrees of freedom, while slightly improving overall propulsive efficiency. The study also highlights the critical role of mass distribution in manta-bots, noting that excessive focus on complex pectoral fin movements and large fin mass can significantly reduce thrust by increasing vertical displacement, ultimately proving counterproductive.

Deterministic particle method for Fokker–Planck equation with strong oscillations

Deterministic particle method for Fokker–Planck equation with strong oscillations