Moving Particle Simulation Method Research Articles

Relationship Between Resultant Force Vector Acting on Human Organs From Food Bolus and the Bolus Configuration During Swallowing Using Numerical Swallowing Simulation With Moving Particle SimulationMethod.

This study investigates the forces exerted on organs during swallowing, specifically focusing on identifying forces other than those resulting from direct organ contact. Using a swallowing simulator based on the moving particle method, we simulated the swallowing process of healthy individuals upon the ingestion of thickened foods, which were simulated as shear-thinning flow without yield stress. We extracted the resultant force vectors acting on the organs and shape of the bolus at each time interval. The simulation results confirmed that the bolus originates from tongue movement and is transferred between the oral cavity and pharynx, with each organ's coordinated movements with the tongue occurring at their respective positions, as indicated by the balance of the resultant force vectors. Utilizing the information about the resultant force vectors obtained through simulations, we calculated the physical parameters of impulse, energy, and power. The variations in these physical parameters were aligned with the behaviors of both the biological system and the food bolus during swallowing. The force values calculated from the simulations closely approximate the theoretical values. Furthermore, the forces calculated from the simulations were relatively smaller than the force values derived from pressure information, such as that from high-resolution manometry and tongue pressure sensors. This difference can be attributed to the simulations extracting only the forces exerted on the organ by the food bolus. Force information on organs has the potential to provide a new interpretation of conventional mechanical indicators such as manometry and tongue pressure sensors.

Simulation of a Pelton turbine using the moving particle simulation method: application to two challenging situations

ABSTRACT Simulation of the flow in a Pelton turbine is a challenging task for mesh based methods due to the air/water mixture and the rotation of the runner. Meshless based methods are better suited for such flows and take advantage of the graphical power unit to speed up the calculation. Simulations of a Pelton turbine are carried out using the software Particleworks based on moving particle simulation, which is a meshless method. The efficiency drop due to the ‘falaise’ effect and the erosion of the splitter are computed and compared with either experimental measurements or the literature. The results show that this method is able to capture the tendency of the efficiency drop in agreement with the available data and at a lower computational cost than the mesh based methods. These encouraging results should motivate the community to test and validate such an approach.

Numerical simulation study of hydraulic performance of the ball valve implied in ultra-high head Pelton turbine

Abstract This paper is deal with the hydraulic performance of the ball valve served in ultra-high head Pelton turbine systems, the Moving Particle Simulation method is used for numerical simulation uncommonly instead of the Finite Volume method. A valve rotating range of 0 degree to 90 degree is simulated by the software Particleworks, according to the pressure change through the valve, we get the flow resistance coefficient which is consistent with those of other similar literature. The change of the internal flow distribution can be visually observed. At the small rotation degree, the flow velocity entering the ball valve is very high and the disturbance in flow field is large. With the rotation degree increases, the flow in ball valve and the outlet pipe is gradually stabilized, the pressure difference before and after the ball valve is gradually reduced. It brings reference value for the structure and size design of the ball valve in the future.

Investigation of hydraulic characteristics of Pelton turbine with casing structure using a moving particle simulation method

Abstract This paper reports the initial results of three dimensional simulation of the jet/bucket interactions in the vertical Pelton turbine with different casing structures. The casing is an important part of the Pelton turbine, and a reasonable casing structure can reduce the interaction between the jet and bucket, so as to improve the hydraulic efficiency of the turbine. Previous research has little numerical simulation analysis on the casing. In this paper, a Moving Particle Simulation(MPS) method without grid generation is adopted to compare and analyze the hydraulic characteristics of the runner under the regular hexagonal and circular casing structures. The simulation results show that the hydraulic efficiency of the runner under the hexagonal casing structure is better, and the runner time average torque is improved by 3.09%, which compared with the circular casing. The distribution of free surface flows in the hexagonal casing is analysis, and the obvious interference phenomenon between jets can be observed, which has an important guiding role in the design of the casing structure of Pelton turbine in the future.

Application of Moving Particle Simulation Method on Water-skipping

Inspired by the phenomenon of stone-skipping in life, the problem of continuous water-skipping in trans-media vehicles is widely concerned, which is characterized by multiphase flow-solid coupling, dynamic boundary, liquid surface fragmentation and high impact loads. Based on the Moving Particle Semi-implicit numerical method, this paper investigates the disc’s motion characteristics and liquid surface variation, focusing on the influence of the water entry parameters on the sloshing phenomenon of the water-skipping. The simulation results indicate that the disc water skipping process can be divided into three stages: water entry, sliding and re-flying, during which the disc is with large impact loads and the water surface is with large scale breaking and droplet splashing. With certain rotation velocity, the disc could maintain a smooth water skipping, while there will be a lateral displacement due to the Magnus effect. The larger the water-entry velocity and angel is, the larger impact load is, the faster velocity decay rate is, the larger vacuole area is, and larger the water surface broking area and the droplet splashing is. Predicted water-skipping phenomenon agrees well with the experimental result obtained from high-speed photography.

Applying surface tension as pressure boundary condition in free surface flow analysis by moving particle simulation method

A model that introduces surface tension as a pressure boundary condition, named the surface tension as pressure (STP) model, was developed for free surface flow analyses by the moving particle simulation (MPS) method. The STP model assigns to surface particles the liquid pressure of Laplace’s formula. The model is an alternative to previous models that apply surface tension as volume force such as the continuum surface force model. Problems that appeared when using the volume force models, such as the dependencies of calculation results on particle resolution and pressure gradient accuracy, were solved by using the STP model. Calculations predicted the theoretical values of the internal pressure of a 3D spherical droplet and the oscillation period of a 2D elliptic droplet over a wide range of surface tension coefficients and droplet sizes with errors less than 10%. Since the STP model is easy to implement, does not increase computation cost from previous models, and does not require surface reconstruction or additional marker particles, the model is suitable for practical and large-scale free surface flow problems that involve violent deformation of the liquid surface such as liquid atomization.

Study on incompressible fluid analysis by three-dimensional particle method with finite volume techniques

Simulating violent free-surface flows by particle methods is effective. In recent years, the SPH (Smoothed Particle Hydrodynamics) method and the MPS(Moving Particle Simulation method) method are considered representative especially in the fields of ship engineering and civil engineering but these methods need various artificial parameters in calculation and may have unnatural large numerical oscillation in the calculated pressure values. In order to avoid these problems, the authors have proposed another particle method based on the finite volume techniques. The usefulness of the proposed method in two-dimensional problems has been verified by comparing the pressure fluctuation when a water tank of the two-dimensional model is forcibly oscillated with the corresponding experiment [1]. Therefore, in this research, the authors extended the algorithm so that the calculation formula can be applied to three-dimensional problems. The effectiveness of the calculation is demonstrated by applying to the dam break problem.

비압축성 입자법 내 압력해법에 관한 GPU 가속화에 대한 연구

In the Moving Particle Simulation (MPS) method, which is a gridless particle method with simple algorithm for solving Navier-Stokes equation, insufficient number of particles in the vicinity of boundary has a considerable influence on the numerical calculation, which causes directly the flow field to become unstable and inaccurate. In particular, the Poisson Equation for pressure is solved iteratively at every time step to obtain an approximate solution. This gratly incereases the amount of computation when performing large-scale particle simulations, which requires high-performance computing. The main objective of this study is to develop a GPU(Graphics Processing Unit)-accelerated MPS code using CUDA(Compute Unified Device Architecture) language to solve the Poisson equation. Furthermore in order to compare the performance of the computational speed, a 3-dimensional calculation of broken-dam break problem has been carried out using the GPU-accelerated MPS method. It can be seen that the performance of the speed ratio in the GPU-based code is improved by about 10 times compared to that of the CPU-based code.

Development of explicit moving particle simulation method with applications

Moving particle simulation (MPS) is a Lagrange meshless method capable of simulating complex fluid problems. To improve computational efficiency with a simple algorithm, explicit algorithms have been proposed such as the Weakly Compressible MPS (WCMPS) method. Although accuracy can be fulfilled in WCMPS, instability arises due to pressure fluctuations of the moving particles. In this study, an explicit Poisson Pressure Equation (PPE) was introduced to address particle instability by improving the pressure calculation, referred to as the Weakly Compressible Moving Particle Explicit (WCMPE) method. By predicting pressure through the equation of state for WCMPS, divergence-free condition is conserved without the implementation of small time-steps. Several numerical cases were investigated by the WCMPE method, including 2D jet imping on a solid plate case, oscillating drop, lid driven cavity, rolling tank experiment, sloshing tank simulation and jet impinging from the bottom of a tank. In general, smooth pressure distribution and improved particle stability were obtained with the incorporation of WCMPE.

Numerical simulation of the molten pool stratification using moving particle simulation method

In the design of third generation nuclear power plants, severe accident mitigation is an important feature. In the study of severe accident phenomena, the immigration of the molten core materials involves physical procedures like mixing of multiple materials, melting and solidification, and complex surface flows. With the conventional lump parameter method, the local 3 dimensional behavior of the molten corium can not be simulated. With the Euler based Computational Fluid Dynamics (CFD) method, it is difficult to simulate the mixing and stratification of multiple molten materials, also the free surface flow is hard to capture in the simulation. In the present study, the Lagrangian based Moving Particle Simulation (MPS) method is applied to investigate the stratification of molten pools. The test results of two immiscible fluids are used to validate the MPS method. A polygon wall model is applied in these simulations, which reduces the number of particles used in the simulation and enables to simulate industry relevant cases in 3 dimensions. A simulation of injection of three different molten materials into a stratified molten pool is carried out to analyze a hypothetical severe accident scenario.

MPS‐Based Model to Solve One‐Dimensional Shallow Water Equations

AbstractHere, a moving particle simulation method is presented to spatially integrate the cross‐sectional average shallow water equations using a prediction‐correction procedure for the time discretization. A density‐ratio equation is derived for the water depth computation according to the particle number density concept. The newly derived equation does not miscalculate the water depth in case an incorrect searching radius parameter is adopted, unlike the typical volume‐summation formula in meshless shallow water flows. A new one‐dimensional Spiky kernel function is developed to satisfy the unity condition employed in the Newton‐Raphson iteration to calculate the water depth. Dynamic stabilization is adopted to capture shockwave problems, a case‐independent technique based on the inelastic collision with unequal masses. The convective flux term is eliminated under the Lagrangian framework, and so the momentum is adequately conserved without the need for any special treatment. The proposed scheme maintains the exact C‐property, meaning that the water depth gradient and bed slope are hydrostatically well balanced within a discretized solution domain. Compared to analytical solutions and experimental data, the results of this study reveal that the present model is a robust numerical solver without unphysical oscillations. It can capture various shock problems, including steep gradient shock‐front, discontinuous wet bed, transcritical flow regimes, and irregular bed topography. The present model can also simulate the dry‐wet flow transition influenced by friction without experiencing any divisions by zero, negative values, or unphysical perturbations. This advantage is basically due to the water particles' absence and presence for the dry and wet regions, respectively.

Application of Moving Particle Simulation Method to Concentric Oil Film in Journal Bearings

Application of Moving Particle Simulation Method to Concentric Oil Film in Journal Bearings

An explicit MPS/FEM coupling algorithm for three-dimensional fluid-structure interaction analysis

Currently, accurate simulations of fluid structure interaction (FSI) problems still remain a challenging task in the academic community. The purpose of this work is to develop a three-dimensional (3D) coupling algorithm to achieve the end, where the explicit moving particle simulation method (MPS) and the finite element method (FEM) are respectively employed to account for fluid flows and structural deformation. The developed coupling algorithm inherits the advantages of the aforementioned methods, while also addressing their shortcomings. We start by extending a newly proposed ghost cell boundary (GCB) model, which has proved to be an effective method to deal with the wall boundary of complicated shapes, to three dimensions. For the problems of interest, the finite elements for structural discretization serve as ghost cells for interaction force calculation, thereby providing an easy and natural way for the construction of ghost cells. The interactions between fluids and structures are dealt with using an integral version of the MPS model, and the resultant interaction forces calculated at integration points of a cell are distributed to finite element nodes for the update of nodal kinematics in the context of an explicit time integration scheme. The effectiveness and accuracy of the 3D GCB model are validated via two numerical examples, i.e., the dam break test and the water flow in a rotating gear test. Afterwards, the developed coupling algorithm is applied to two common FSI problems, i.e., the dam break tests with respective an elastic obstacle and an elastic gate. The good agreements between our simulation results and the existing data in literature demonstrate the accuracy and capacity of the developed coupling algorithm in solving FSI problems.

A novel ghost cell boundary model for the explicit moving particle simulation method in two dimensions

The moving particle simulation (MPS) method has proved to be an effective technique to model fluid flows with free surfaces. However, it still remains a challenging task to treat the wall boundary problem with complicated geometries accurately and robustly. The purpose of this work is to propose a two-dimensional ghost cell boundary model for the explicit MPS method to achieve this end. The appeal of the novel model lies in providing an easy and natural treatment for the wall boundary of complicated shapes. On one hand, the wall boundary can be easily represented by using ghost cells of different sizes or shapes (e.g. triangles and quadrilaterals in two dimensions), and ghost cells are constructed in the pre-processing phase. On the other hand, the particle-cell interaction can be modeled by an integral version of the MPS model that requires the specific area of each cell, while the particle-particle interaction near wall boundary is still handled by the conventional version of the MPS model via assuming that each particle takes the same area. In this manner, the particle-cell interaction is modeled naturally. Two numerical examples, i.e. the hydrostatic and dam break tests, are performed to validate the effectiveness of the proposed model, where the effects of the distribution of ghost cells are also numerically investigated. Finally, a numerical case considering a star-shaped obstacle in dam break flows is carried out to demonstrate the capacity of the novel model in dealing with the wall boundary problem with complicated geometries.

Flowing behavior with several kinds of filters using water experiment and MPS (Moving Particle Simulation) method

Flowing behavior with several kinds of filters using water experiment and MPS (Moving Particle Simulation) method

Numerical Simulation of 2-D Solitary Wave Run-Up over Various Slopes Using a Particle-Based Method

The present paper covers the numerical prediction of the propagation and run-up of a solitary wave over non-flat seabed with various slope angles using a refined MPS (moving particle simulation) method. In the refined method, the corrected gradient model, new staggered divergence-free model, moving-particle wall boundary treatment, and the sub-particle scale turbulence model are applied to obtain more stable and precise results. The simulation results by the developed method are compared with experimental results, and both results were in good agreement. Especially, it can be seen that the complicated and fully-nonlinear behavior of the free-surface motion during the turbulent processes of build-up, break-down, and overturning of the waves are well reproduced by the developed method.

Interaction Simulations Between Fluids and Complicated Structures Using EMPS-FEM

The interactions between fluids and complicated solid structures are common phenomena in practical engineering applications, e.g., water-tire interaction in the hydroplaning problem. In this work, we advocate the coupled explicit moving particle simulation method and the finite element method (EMPS-FEM) to solve this problem, where the EMPS is used to describe the fluid flow and the FEM is for structural deformation. In the existing EMPS-FEM method, the interface interaction between the fluid and the structure is solved by an explicitly represented polygon (ERP) wall boundary model. For the situations with complicated solid structures, e.g.,angled edges, the ERP model attempts to address the particle leakage problem by adding repulsive forces to the particles. However, numerical inaccuracy and instability may arise in this model, because only the repulsive force contributed by the nearest polygon is considered for each particle undergoing leakage. The purpose of this work is to develop a robust and accurate EMPS-FEM coupling approach based on the ERP wall boundary model. Special attention is paid to the interaction situations with complicated solid structures. Numerical examples are performed to validate the effectiveness of the proposed algorithm.

High-performance computing in simulation of milk crown

A high-performance computation with billion scales of the explicit moving particle simulation method is successfully performed for the milk crown phenomena. Through the validation study regarding the size of the particle, it is confirmed that the appropriate size for realizing milk crown should be smaller than 0.05 mm. The simulation results are rather in good agreement with the experimental ones. Namely, the tiny droplet at the tip of the milk crown, which is called the spike, and the generation of spear-type splash, which is the secondary splash formed after the milk crown, are realized well as seen in the experiment.

Numerical visualisation of physical values during human swallowing using a three-dimensional swallowing simulator ‘Swallow Vision®’ based on the moving particle simulation method

ABSTRACTThe aim of this study is to visualise changes in physical values of food bolus during swallowing to correlate the movement of human organs and bolus flow configuration using Swallow Vision®, a three-dimensional human swallowing simulator. Swallow Vision was developed using realistic human organ models, food bolus models, and the meshless three-dimensional moving particle simulation (MPS) method. The human organ model used to create Swallow Vision was reconstructed using computed tomography and video-fluorography images of a healthy volunteer. The extracted physical values, such as velocity, shear rate and viscosity were correlated with the movement of human organs and bolus flow configuration. The velocity and the shear rate were in good agreement with other researchers’ results, and the simulation results are hence considered adequate. Swallow Vision will be helpful for understanding swallowing biomechanics, as well as for identifying appropriate foods for people with swallowing difficulties or dysphagia.

Numerical model for non-Darcy flow through coarse porous media using the moving particle simulation method

A numerical model for non-Darcy flow, which occurs when water moves through coarse porous media under high Reynolds number, is developed. The governing equation for incompressible viscous flow through porous media is composed of a continuity equation and a momentum equation, which is the Navier-Stokes equation with an additional non-linear resistance term based on Forchheimer?s law. For the discretization scheme, moving particle simulation method is employed. In order to assess the model validity, seepage experiments in different kinds of coarse porous media are implemented, and then reproducibility of the numerical results is examined. From the results, it is found that the computational flow velocities at middle part of porous media are in good agreement with experimental ones while velocities at outflow end are overestimated.