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The paper is focused on problem of filtering random processes in dynamical systems whose mathematical models are described by stochastic differential equations with a Poisson component. The solution of a filtering problem supposes simulation of trajectories of solutions to a stochastic differential equation. The trajectory modelling procedure includes simulation of a Poisson flow permitting application of the maximum cross section method and its modification. [ABSTRACT FROM AUTHOR]

This work is devoted to the numerical simulation of the Bhatnagar--Gross--Krook (BGK) equation for two species in the fluid limit using a particle method. Thus, we are interested in a gas mixture consisting of two species without chemical reactions assuming that the number of particles of each species remains constant. We consider the kinetic two species model proposed by Klingenberg, Pirner, and Puppo in [Kinetic Rel. Models, 10 (2017), pp. 445-465], which separates the intra- and interspecies collisions. We want to study numerically the influence of the two relaxation terms, one corresponding to intraspecies and the other to interspecies collisions. For this, we use the method of micro-macro decomposition. First, we derive an equivalent model based on the micro-macro decomposition (see Bennoune, Lemou, and Mieussens [J. Comput. Phys., 227 (2008), pp. 3781-3803] and Crestetto, Crouseilles, and Lemou [Kinetic Rel. Models, 5 (2012), pp. 787-816]). The kinetic micro part is solved by a particle method, whereas the fluid macro part is discretized by a standard finite volume scheme. The main advantages of this approach are that (i) the noise inherent to the particle method is reduced compared to a standard (without micro-macro decomposition) particle method, and (ii) the computational cost of the method is reduced in the fluid limit since a small number of particles is then sufficient. [ABSTRACT FROM AUTHOR]

Ice and snow are usually classified as a viscoelastic or viscoplastic materials according to temperature, strain rate, pressure and time scale. Throughout experimental studies presented in the literature, it has been observed that at very low temperatures or high strain rates, porous ice and snow exhibit brittle behavior, but experience high viscous and plastic flow at temperatures close to the melting point and low rates. At the macroscopic level, nonlinearity is not necessarily attributed to permanent changes in the material or yielding but mainly to micro cracks, intergranular sliding, porosity collapse and crack propagation. In this paper, this complex behavior is described with a full microstructure-based model. Classical rheological models and beam theory are used to describe aspects of creep and fracture of granular ice and snow. [ABSTRACT FROM AUTHOR]

The last decades have witnessed sharp progress in both numerical simulation methods and computing power. Realistic simulation of complex structures such as snow remains challenging. The discrete particle approach now accessible due to advances in parallel processing has shown to be a good alternative for brittle and quasi-brittle materials. A novel numerical model has been described in part I of this study. Ice grains in snow are found near their melting points with an enhanced creep that constantly affects its microstructure. The behavior of snow combines characteristics of polycrystalline ice, which depends on stress rate, temperature, hydrostatic pressure and geometrical proprieties that affects its fracture properties. Snow can pass from porous continuous structure to a granular form or creep intensively when loaded. The herein proposed methodology includes time and pressure dependent bonding properties of ice and predicts large displacements, fracture, and granular flow in snow under the effect of mechanical stress. A micromechanical approach based on particle mechanics and beam theory is used to capture microstructure evolution under external loads. The calibration and validation are based on stress-strain data from some compression tests found in the literature. [ABSTRACT FROM AUTHOR]

Based on a stochastic microscopic collisional model of the motion of charged particles in a strong external magnetic field, a hierarchy of equations of magnetic hydrodynamics is constructed. The transition to increasingly rough approximations occurs in accordance with a decrease in the dimensioning parameter, similar to the Knudsen number in gas dynamics. The result is stochastic and nonrandom macroscopic equations that differ from the magnetic analog of the Navier–Stokes system of equations, as well as from the systems of magnetic quasi-hydrodynamics. The main feature of this derivation is more accurate velocity averaging due to the analytical solution of stochastic differential equations with respect to the Wiener measure, in the form of which the intermediate meso model is presented in the phase space. This approach differs significantly from the traditional one, which uses not the random process itself but its distribution function. Emphasis is placed on the clarity of assumptions when moving from one level of detail to another, and not on numerical experiments that contain additional approximation errors. [ABSTRACT FROM AUTHOR]

In computational fluid dynamics there have been many attempts to combine the advantages of having a fixed mesh, on which to carry out spatial calculations, with using particles moving according to the velocity field. These ideas in fact go back to particle-in-cell methods, proposed about 60 years ago. Of course, some procedure is needed to transfer field information between particles and mesh. There are many possible choices for this "assignment", or "projection". Several requirements may guide this choice. Two well-known ones are conservativity and stability, which apply to volume integrals of the fields. An additional one is here considered: preservation of information. This means that assignment from the particles onto the mesh and back should yield the same field values when the particles and the mesh coincide in position. The resulting method is termed "mass" assignment, due to its strong similarities with the finite element method. Several procedures are tested, including the well-known FLIP, on three scenarios: simple 1D convection, 2D convection of Zalesak's disk, and a CFD simulation of the Taylor–Green periodic vortex sheet. Mass assignment is seen to be clearly superior to other methods. [ABSTRACT FROM AUTHOR]

Fluid–structure-interaction (FSI) phenomena with multi-phase flow dynamics and structural damage commonly exist in engineering practice, which however bring great challenges to nowadays numerical FSI algorithms. A novel localized subdomain smoothing MMALE particle method (ls-ALEPM) is proposed in this paper for efficient and accurate simulations of large scale FSI problems. The MMALE method and the MPM are strongly coupled by immersing the MPM particles into the MMALE grid. In order to avoid the spurious strain induced by the mixed FSI velocity field, a decoupled stress updating scheme is proposed to update the stress of solid particles by introducing a virtual velocity field in the vicinity of FSI interface. And specifically, the highly accurate polyhedron intersection based method is employed for its remapping phase, which however is time-consuming. Thus, the localized subdomain smoothing method (LSSM) is put forward to accelerate the remapping phase which only involves the distorted regions of computational grid. The LSSM is composed of a distorted subdomain determination step and a combinated mesh smoothing step. Each iteration of the combinated mesh smoothing step consists of the modified GETMe and the weighted average method, and the transfinite interpolation method is adopted if the quality criteria is still not satisfied after prescribed maximum number of iterations. The validity and efficiency of ls-ALEPM is verified by several benchmark numerical examples and practical engineering simulations. [ABSTRACT FROM AUTHOR]

This paper presents a new macroscopic mesh-free particle method in which Darcy’s and Forchheimer’s terms are introduced into the governing equation to ensure the capacity of the particle method in simulating laminar and turbulent porous medium flows. A developed interfacial condition and inflow boundary condition are implemented in the macroscopic particle method to improve the stability of the Particle-based model. The comparisons of channel flow over and within porous bed among the present method, previous mesh-based method, and experimental data show that the macroscopic particle method is capable of simulating flows in both the clear flow region and porous flow region. Finally, two cases of flow over a rigid box and a cylinder lying on porous bed are simulated, and the numerical results are in good agreement with the measured data. The analysis and comparisons indicate that the newly developed particle-based method is reliable and has been successfully extended to macroscopic porous medium simulation.

Understanding the damping mechanism of baffles is helpful to make more reasonable use of them in suppressing liquid sloshing. In this study, the damping effect and mechanism of vertical baffles in shallow liquid sloshing under a rotational excitation are investigated by an improved particle method. By incorporation of a background mesh scheme and a modified pressure gradient model, the accuracy of impact pressure during sloshing is significantly enhanced. Combined with the advantages of the particle method, the present numerical method is a wonderful tool for the investigation of liquid sloshing issues. Through the analysis of impact pressure, the influences of baffle height and baffle position on the damping mechanism are discussed. The results show that the damping effect of vertical baffles increases with the increase of the elevation of baffle top and decreases with the increase of the elevation of the baffle bottom. Moreover, the resonance characteristics of sloshing are altered when static water is divided into two parts by the vertical baffle. The dominant damping mechanism of vertical baffles depends on the configurations.

In this work the first 3D Smoothed Particle Hydrodynamics model of a Rayleigh collapse for an empty cavity is proposed with the aim of improving the hydrodynamic analysis of a non-symmetrical collapse. The hydrodynamics of the model is validated against the solution of the Rayleigh-Plesset equation for a symmetrical collapse. The model is then used to simulate a non-symmetrical collapse of an empty cavity attached to a solid surface with γ=0.6 induced by an external pressure of 50 [MPa]. The results shows that is possible to identify three regions where the hydrodynamics of the collapsing cavity shows different features. For all the stages of the collapse the simulation shows smooth pressure and velocity fields in the liquid and in the solid phase with the formation of a vortex ring in the final phase of the collapse. Finally, the model is compared to a previous 2D model to highlight strong, weak points and the key differences of both approaches in final phase of the collapse.

In this paper, we proposed a new particle method for numerical simulation of droplet dynamics. In the proposed method, the moving surface mesh is used to define interface between gas and liquid. The volume enclosed by the mesh represents the liquid droplet, and the outer domain is inactive gas with constant pressure. The incompressible liquid flow is calculated using a particle method, in which spatial derivatives are evaluated using an arbitrary high order accurate scheme. On the free surface, the surface stress balance equations, including surface tension and viscous stress, are adopted for the boundary conditions. Deformation of the gas-liquid interface is explicitly calculated by surface nodes that move in a Lagrangian fashion. Surface tension force is directly evaluated with high accuracy on each node utilizing the mesh shape. As numerical verification, simulations of three benchmark problems, namely circular patch test, Laplace pressure test and 2D droplet (liquid column) oscillation problems with different oscillation modes, have been carried out. The computation results were compared with the theoretical solutions, and excellent agreements were obtained. As a result, high accuracy and validity of the proposed computational method were confirmed.

The authors have generalized the mathematical formalism of hybrid particle method (method of hybrid cellular automata) for the numerical simulation of deformation and fracture of fluid-saturated porous geological materials at the meso- and macroscopic scales. The formalism allows taking into account inelastic deformation, dilatancy and fracture of solid skeleton as well as the influence of pore pressure on skeleton stress state and the fluid redistribution in pore space of the fractured geological medium. In the framework of the model the mechanical response of the skeleton is described within the model of plasticity of geological medium with unassociated flow law. The redistribution of the gas phase is simulated by numerical solution of equations of filtration and diffusion. The adequacy of the formalism is illustrated with the results of the theoretical study of gas pore pressure influence on coal sample strength under uniaxial compression. It is shown that the degree of pore pressure influence on macroscopic strength of gas-saturated material is strongly determined by the ratio of parameters of strength criterion, which reflects the content of defects and damages of high rank in the solid skeleton.

LAMMPS is a powerful simulator originally developed for molecular dynamics that, today, also accounts for other particle-based algorithms such as DEM, SPH, or Peridynamics. The versatility of this software is further enhanced by the fact that it is open-source and modifiable by users. This property suits particularly well Discrete Multiphysics and hybrid models that combine multiple particle methods in the same simulation. Modifying LAMMPS can be challenging for researchers with little coding experience. The available material explaining how to modify LAMMPS is either too basic or too advanced for the average researcher. In this work, we provide several examples, with increasing level of complexity, suitable for researchers and practitioners in physics and engineering, who are familiar with coding without been experts. For each feature, step by step instructions for implementing them in LAMMPS are shown to allow researchers to easily follow the procedure and compile a new version of the code. The aim is to fill a gap in the literature with particular reference to the scientific community that uses particle methods for (discrete) multiphysics.

Summary: In this paper, simple and consistent open boundary conditions are presented for the numerical simulation of viscous incompressible laminar flows. The present approach is based on an arbitrary Lagrangian‐Eulerian particle method using upwind interpolation. Three kinds of inlet/outlet boundary conditions are proposed for particle methods, a pressure specified inlet/outlet condition, a velocity profile specified inlet/outlet condition, and a fully developed flow outlet condition. These inlet/outlet conditions are realized by using boundary particles and modification to the physical value such as velocity. Poiseuille flows, flows over a backward‐facing step, and flows in a T‐shape branch are calculated. The results are compared with those of mesh‐based methods such as the finite volume method. The method presented herein exhibits accuracy and numerical stability. [ABSTRACT FROM AUTHOR]

In this study, we propose a smoothed particle hydrodynamics model for simulating a shock wave interacting with cylindrical gas inhomogeneities inside a shock tube. When the gas inhomogeneity interacts with the shock wave, it assumes different shapes depending on the difference in densities between the gas inhomogeneity and the external gas. The model uses a piecewise smoothing length approach and is validated by comparing the results obtained with experimental and CFD data available in the literature. In all the cases considered, the evolution of the inhomogeneity is similar to the experimental shadowgraphs and is at least as accurate as the CFD results in terms of timescale and shape of the gas inhomogeneity. [ABSTRACT FROM AUTHOR]

In this paper, we developed a GPU parallelized Total Lagrangian Formation of Smoothed Particle Hydrodynamics (TLSPH) algorithm for 3D geometrical nonlinear structure analysis. The code was developed using NVDIA CUDA C++. Both the TLSPH and GPU parallelization algorithms are described in detail. Compared to the traditional FEM method for structure analysis, TLSPH method is much easier to be implemented and parallelized. In addition, as a meshless based method, there is no need to mesh the domain for TLSPH method. Also, the computational cost of TLSPH is much lower than the Weakly Compressible Smoothed Particle (WCSPH) method. By introducing GPU acceleration, we have significantly improved the code performance. Two benchmark test cases for 3D geometrical nonlinear structure analysis are carried out. The simulation results are compared with analysis results and the data obtained by Abaqus, which is a popularly-used software for structure analysis based on FEM method. In order to show the efficiency of GPU parallelization, a serial code based on the same TLSPH method is also developed as a reference. Results show GPU parallelization accelerates the code obviously. In summary, the GPU parallelized TLSPH method shows the potential to become an alternative way to deal with 3D geometrical nonlinear structure analysis. [ABSTRACT FROM AUTHOR]

In high-pressure die casting (HPDC) processing of aluminum alloys, solidified layers generated in the sleeve of a die casting machine that flow into the mold cavity are known as "cold flakes." The prediction and control of them are a crucially important issue for HPDC. This study developed a method to simulate their formation and flow using smoothed particle hydrodynamics. First, a solidified layer was modeled as a set of solid particles with behaviors defined by mechanical constitutive equations. Second, this study proposed an algorithm for ascertaining the phase of particles and for calculating liquid–solid particle interaction. Numerical results demonstrated that the method can predict the formations of solidified layers in the sleeve, their peeling and folding during the plunger movements, their inflow into the runner and the mold cavity, and flow disturbances caused by solidified layers trapped at the gate. [ABSTRACT FROM AUTHOR]

The paper is devoted to studying the features of the discontinuous particle method. The algorithmic fundamentals of the particle method are described in detail. The possibility of using limiters is investigated. The results of the calculations for the Hopf, Burgers, shallow water, and gas dynamics' equations, including nonlinear acoustics, are presented. The numerical solutions are compared with some exact ones. The tests show that the method is suited for problems with discontinuities. It is shown that in order to obtain a more accurate numerical solution, it is necessary to refine the initial mathematical models. In other words, for the problem of the structure of the front of the shock wave if we take the equations of stochastic gas dynamics instead of the Navier-Stokes equations, then the need for limiters disappears. [ABSTRACT FROM AUTHOR]

The Escalator Boxcar Train (EBT) numerical method has been designed and widely used by theoretical biologists to compute solutions of one-dimensional structured population models of McKendrick--von Foerster type. Recently the method has been derived for an age-structured twosex population model (Fredrickson--Hoppenstaedt model), which consists of three coupled hyperbolic partial differential equations with nonlocal boundary conditions. The convergence of the EBT method for the Fredrickson--Hoppenstaedt model has not been analyzed, and relevant numerical examples are still missing. In this paper, we derive a simplified EBT method for the "two-sex model" and prove its convergence. However, due to the interest in tracking specified cohorts of individuals, the analytical results cannot be analyzed in the L1 norm. Instead, we embedded the problem in the space of nonnegative Radon measures equipped with the bounded Lipschitz distance (the flat metric). We also present numerical examples to illustrate the results, compute the error in bounded Lipschitz distance, and compare it against the total variation (TV) distance. [ABSTRACT FROM AUTHOR]

Since the 12 May 2008 Wenchuan earthquake, numerous catastrophic debris flows have occurred in the Wenchuan earthquake-stricken zones. In particular, on 14 August 2010, long-duration, low-intensity rainfall triggered widespread debris flows at the epicenter of the Wenchuan earthquake. These flows caused serious casualties and property losses. In this study, a novel approach combining a soil-water mixing model and a depth-integrated particle method is applied to the analysis of the post-seismic debris flows in the epicentral area. The presented approach makes use of satellite images of the debris flow in the affected area. It is assumed that debris source materials are primarily generated from slope failure during the earthquake. Debris flows are initiated after different amounts of cumulative rainfall according to diffusion governing equations. The debris flow disaster is investigated in terms of volume, concentration, discharge, velocity, deposition thickness and affected area by setting the cumulative rainfall, Manning coefficient and diffusion coefficient to 38 mm, 0.1 and 0.004 m2 s−1, respectively. Although the thickness and volume of debris source materials are underestimated in this study, the numerical results, including the volume concentration, velocity, discharge and the affected area are in good agreement with the actual observations/measurements of the debris flow events. Adopting a simple and efficient numerical model, systematic analysis of the entire debris flow generation process not only contributes to understanding the mechanism of initiation, transportation and deposition, but is also very useful in designing effective protection structures according to the distribution characteristics of the main parameters. Additionally, the coupling effect of multiple debris flows is discussed. [ABSTRACT FROM AUTHOR]

The processes of charge transfer in semiconductors are considered. A model is constructed based on the quantum kinetic equations for the distribution functions of conduction electrons and holes of the valence band in the phase space of coordinates and quasi-momenta. Scattering of charge carriers is modeled by the statistical particle method. The basic processes of electron scattering by lattice defects are considered. The calculations of the electron drift velocity in pure and doped silicon are presented. [ABSTRACT FROM AUTHOR]

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Since particle-based computational methods, such as smoothed particle hydrodynamics (SPH) method, are suitable to treat free surfaces and moving boundaries, it is expected that the simulation with particle methods can represent more accurate molten metal flow. Hence, we apply the SPH method to some casting processes and validate the numerical results by comparing with experiments. While fluid behaviors of the transportation and the mold filling processes are expressed sufficiently, ladle pouring process of aluminum alloy is not reproduced by the existing scheme. So we developed a new numerical model of surface oxide film, and our numerical results show good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

In this study, the impacting force on the face of porous structure is investigated by using the mesh-free macroscopic model. To achieve this, the mesh-free macroscopic approach of Moving Particle Semi-implicit method (MPS) is redeveloped. Firstly, a stabilization technique is used in the method to eliminate numerical noise. Secondly, the spatial discretization operators employ a porosity-based coefficient to account for the representative volume to model fluid flows in the porous media. More importantly, an improved numerical technique is proposed to overcome abrupt porosity change at the boundary between the porous and non-porous regions. The numerical model is validated by the dam-breaking waves through porous blocks and flows over porous weirs, in which the simulated free-surface profiles are in good agreement with experimental measurements. By applying the method, how the porosity and mean diameter of porous materials play a role in impacting pressure and wave height for dam-breaking flow through porous block is investigated. It is found that the porous materials with a larger porosity or larger mean diameter are able to easily permit water penetration through the porous media while the impacting pressure at the interface and reflected wave height can be reduced. • The impacting force on the face of porous structure is investigated. • An improved interface treatment for porosity discontinuity in modeling porous and non-porous phase is proposed. • The proposed interface treatment can reduce the required length of a zone to achieve continuous porosity variation. • The numerical method can simulated good results for flow through porous media. [ABSTRACT FROM AUTHOR]

The influence of electron-ion collisions on breaking cylindrical nonlinear plasma oscillations is studied. Numerical calculations by the particle method and an analytic analysis by the perturbation method in the weak nonlinearity regime show that, with an increasing collision frequency, the time needed to break plasma oscillations increases. The threshold value of the collision frequency is found exceeding which the density singularity does not arise. In this case, the maximum of the electron density formed outside the axis of the oscillations, the growth of which in the regime of rare collisions leads to the breaking effect, after some growth begins to decrease due to the damping of the oscillations. [ABSTRACT FROM AUTHOR]

Abstract The variation of physical properties across the interface and the inaccuracy of spatial derivative on discontinuity contribute to the numerical instability in multiphase flow with large density or viscosity ratio. With integral basic equation in Peridynamic theory under updated Lagrangian formulation and stress tensor calculation by Moving Particle Semi-implicit method(MPS), a new numerical approach on dealing with the abrupt physical quantities is introduced. Besides, a modified matrix inspired by the shape function in Peridynamics is added in the gradient and divergence operators to eliminate the error caused by irregular particle distribution. In addition, to decrease the calculation error caused by large properties difference, a decomposition process on the stress tensor and its divergence are proposed, the large acceleration difference by the discontinuity of density on the interface is smoothed after a mean density and the accuracy is validated by a simple example. Four benchmark cases, oscillating two-layer elliptical region, Rayleigh–Taylor instability, two-phase dam-break and bubble rising examples, are simulated to demonstrate the feasibility and accuracy of the proposed method in multiphase flow with both small and large physical quantity ratio. [ABSTRACT FROM AUTHOR]

Highlights • A novel algorithm calculating viscosity after pressure is proposed for MPS. • Numerical creeping of highly viscous fluid is eliminated by the new algorithm. • Viscosity escalation can reasonably represent crust formation with the new algorithm. • VULCANO VE-U7 experiment demonstrates improvement of the new algorithm. Abstract Corium (lava-like mixture of fissile material) spreading prediction is of great significance in the severe accidents of nuclear power plants. Crust formation due to solidification distinguishes corium spreading from common isothermal spreading. The Lagrangian moving particle semi-implicit (MPS) method is potential for such spreading flow with both free surface and crust-melt interface. Crust formation is usually represented by viscosity escalation, but crust creeping is an associated problem. In the original MPS algorithm, creeping velocity cannot be reduced steadily by the continuous increase of viscosity, owing to the numerical creeping. A new solution algorithm is proposed for particle methods to eliminate such numerical creeping, so that creeping velocity decreases proportionally with viscosity rise. In this situation, high enough viscosity can effectively represent crust behaviors. Three numerical examples, leakage flow with high viscosity, dam break flow with low viscosity and the VULCANO VE-U7 corium spreading experiment with both high and low viscosities simultaneously, are investigated to contrast the performance difference between the original and new algorithms. It is demonstrated that the current algorithm is suitable for crust formation in corium spreading. [ABSTRACT FROM AUTHOR]

This paper aims to discuss the boundary conditions techniques employed in the solution of physical and engineering problems using the Lagrangian particle approach in continuum mechanics. Simulations using different boundary treatment techniques have been performed, and in addition, a review of the literature on the techniques commonly employed in SPH simulations was also performed. The fictitious (virtual/ghost), the dynamic particles and the artificial repulsive forces are widely employed in problem-solving, mixing concepts of molecular and continuum scales, being inadequate for the use in continuum scale (considering the disrespect of the classical physics laws). On the other hand, the reflective boundary conditions, based on fundamentals of Physics (Newton's restitution law) and analytic geometry, are in accordance with the continuum hypothesis and their use is recommended in continuum mechanics problems, out of the molecular scale. In many boundary conditions employed in particle methods, models of repulsive molecular forces in conjunction with virtual particles are being used without theoretical foundation in continuum mechanics and classical Physics. Purely computational solutions employing fictitious particles and artificial molecular forces should be avoided, and methods that respect the continuum theory, such as the reflective boundary conditions, should be employed on the macroscopic scale. Both hydrostatic and hydrodynamics analysis have been performed. An excellent agreement with the analytical solution or experimental results have been achieved. From the results found, the applicability of the reflexive boundary technique in the continuum domain, discretized by particles, was verified. [ABSTRACT FROM AUTHOR]

The applicability of experimental and numerical models used for the solution of dam-break flows is vital for better dam projects and also in preventing related accidents. The high cost and the time-consuming nature of laboratory studies require consistency in the investigation of numerical models. In this study, the propagation of a flow using a fluid with a different density from that of normal water in the reservoir was investigated both experimentally and numerically. Salt water was preferred as a Newtonian fluid in order to observe the propagation of flows in different density after a sudden break. A small-scale channel was constructed and laboratory data were obtained using image processing techniques. For the numerical model, Smoothed-Particle Hydrodynamics (SPH) method and Reynolds Averaged Navier-Stokes (RANS) equations solved by Flow-3D software, were applied. Flow depth changes were observed in the reservoir and the downstream. The data obtained from all methods were compared with each other. The results of two numerical simulations point out that the disagreements on graphs in the time evolutions of the fluid levels in the SPH increase due to turbulence effects, whilst, these differences decrease in the RANS equations solved by Flow-3D software. Consequently, since the SPH provides taking the measures and developing intervention strategies to reduce the risks connected to the evolution of dam-break flows, it is thought that future validation studies of the model will be require with the use of data observed in this field. [ABSTRACT FROM AUTHOR]

The non-symmetrical collapse of an empty cylindrical cavity is modeled using Smoothed Particle Hydrodynamics. The presence of a nearby surface produces an anisotropic pressure field generating a high-velocity jet that hits the surface. The collapse follows a different dynamic based on the initial distance between the center of the cavity and the surface. When the distance is greater than the cavity radius (detached cavity) the surface is hit by traveling shock waves. When the distance is less than the cavity radius (attached cavity) the surface is directly hit by the jet and later by other shock waves generated in the last stages of the of the collapse. The results show that the surface is hit by a stronger shock when distance between the center of the cavity and the surface is zero while showing more complex double peaks behavior for other distances.

Lee, B.H. and Kim, K.S., 2023. The effects of active sloshing reduction device on vessel motions. In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 553-557. Charlotte (North Carolina), ISSN 0749-0208. The impact of sloshing effects due to inner liquid cargo has long been recognized as a crucial parameter in the design stage, spanning decades. Numerous research and engineering literatures have emphasized how these effects can alter the motions of floating bodies, including their natural frequencies. The recognition of sloshing effects has prompted investigations into utilizing them positively, leading to initiatives like the development of anti-rolling tanks. This study delves into the exploration of anti-rolling tanks using the Moving Particle Semi-Implicit (MPS) method. The effects of these tanks on vessel motions are considered through a dynamically coupled problem employing the Boundary Element Method (BEM). The sloshing effects on vessel motions are demonstrated, and their positive implications, such as motion control and manipulation of the vessel's natural frequency, are thoroughly examined. The findings reveal that the natural phenomena of the vessel can be effectively controlled by adjusting sloshing reduction effects. This not only highlights the significance of considering sloshing effects in vessel design but also underscores the potential for utilizing them to actively control and manage vessel motions for improved performance and stability. [ABSTRACT FROM AUTHOR]

Kim, K.S., 2023. Numerical modeling of solid particle dynamics using the Moving Particle Semi-Implicit (MPS) method in seabed penetration scenarios. In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 548-552. Charlotte (North Carolina), ISSN 0749-0208. The Moving Particle Semi-Implicit (MPS) method, a particle-based approach within computational fluid dynamics, underwent development and modification to effectively model the behavior of solid particles. To address phenomena associated with solid particles, the traditional viscosity calculation term was replaced with a friction calculation term that accounts for accumulated weight effects. The resulting program was employed to simulate the behavior of soil in a seabed penetration scenario. Subsequently, numerical outcomes were compared with corresponding experimental results to validate the efficacy of the newly developed approach. [ABSTRACT FROM AUTHOR]

Viscoelastic bonds intended for Discrete Multiphysics (DMP) models are developed to allow the study of viscoelastic particles with arbitrary shape and mechanical inhomogeneity that are relevant to the pharmaceutical sector and that have not been addressed by the Discrete Element Method (DEM). The model is applied to encapsulate particles with a soft outer shell due, for example, to the partial ingress of moisture. This was validated by the simulation of spherical homogeneous linear elastic and viscoelastic particles. The method is based on forming a particle from an assembly of beads connected by springs or springs and dashpots that allow the sub-surface stress fields to be computed, and hence an accurate description of the gross deformation. It is computationally more expensive than DEM, but could be used to define more effective interaction laws.

The particle methods are suited to simulate fluid flow problems with large boundary deformation. The moving particle semi-implicit (MPS) method is one of the representative particle methods for incompressible flow. In recent years, the MPS method has received a great deal of attention in various fields of science and engineering. However, the numerical treatment of complicated wall geometry is still an open question. The conventional approaches have severe issues in handling arbitrary shape or calculation accuracy. In these circumstances, this study has been done to propose a novel numerical treatment of solid wall boundary in the MPS method. In this approach, the wall contribution in the discretization scheme is described in a form of volume integral over object domain. Thus, arbitrary-shaped boundaries represented by a polygon mesh can faithfully be considered. Moreover, since the distribution of physical quantity inside object is given by linear extrapolation, it satisfies the prescribed boundary condition with high accuracy. While the volume integral cannot be numerically evaluated with affordable computational cost, it can be transformed into a boundary integral form based on the divergence theorem. The derived boundary integral can be calculated with reasonable cost and acceptable accuracy using a projection technique and the Gaussian quadrature. The proposed method has been examined through several numerical test cases in 2D and 3D. As a result of the numerical tests, the present method is shown to have considerably higher accuracy compared to conventional methods, and its validity is verified.