Simulation Of Particle Motion Research Articles

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

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.

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.

An Efficient Explicit Moving Particle Simulation Solver for Simulating Free Surface Flow on Multicore CPU/GPUs

The moving particle simulation (MPS) method is a simulation technique capable of calculating free surface and incompressible flows. As a particle-based method, MPS requires significant computational resources when simulating flow in a large-scale domain with a huge number of particles. Therefore, improving computational speed is a crucial aspect of current research in particle methods. In recent decades, many-core CPUs and GPUs have been widely utilized in scientific simulations to significantly enhance computational efficiency. However, the implementation of MPS on different types of hardware is not a trivial task. In this study, we present an implementation method for the explicit MPS that utilizes the Taichi parallel programming language. When it comes to CPU computing, Taichi’s computational efficiency is comparable to that of OpenMP. Nevertheless, when GPU computing is utilized, the acceleration of Taichi in parallel computing is not as fast as the CUDA implementation. Our developed explicit MPS solver demonstrates significant performance improvements in simulating dam-break flow dynamics.

Research on rotational resistance in particle motion simulation based on discrete element method

Research on rotational resistance in particle motion simulation based on discrete element method

Novel design modeling for vertical shaft impactors

The purpose of this article is to present a novel mathematical-physical model for the design of a new conical-shaped centrifugal rotor for vertical shaft impact crushers (VSI's) to reduce energy consumption. Many models of flat disced centrifugal rotors have been developed, however, these models do not use mathematical-physical relations to define the particle trajectory on the centrifugal rotor, which corresponds to the curvature of the shape of the centrifugal rotor chambers. The determination of particle movement on the outer mantel of a rotating conical-shaped centrifugal rotor depends on cone geometry, feed material, and operation parameters, which were thoroughly studied to design the new conical rotor. The equations which describe the particle motion on the centrifugal rotor are derived and utilized. The mathematical-physical relation equations were analyzed and given as a solvable model of the particle motion simulation using a program developed in C++ using Microsoft Visual Studio. It can be concluded that in order to improve existing empirical designs, energy consumption must be reduced by improving the material flow rate and avoiding material clogging inside the centrifugal rotor.

Extension of moving particle simulation by introducing rotational degrees of freedom for dilute fiber suspensions

AbstractWe develop a novel Moving Particle Simulation (MPS) method to reproduce the motion of fibers floating in sheared liquids accurately. In conventional MPS schemes, if a fiber suspended in a liquid is represented by a one‐dimensional array of MPS particles, it is entirely aligned to the flow direction due to the lack of shear stress difference between fiber–liquid interfaces. To address this problem, we employ the micropolar fluid model to introduce rotational degrees of freedom into the MPS particles. The translational motion of liquid and solid particles and the rotation of solid particles are calculated with the explicit MPS algorithm. The fiber is modeled as an array of micropolar fluid particles bonded with stretching, bending and torsional potentials. The motion of a single rigid fiber is simulated in a three‐dimensional shear flow generated between two moving solid walls. We show that the proposed method is capable of reproducing the fiber motion predicted by Jeffery's theory which is different from the conventional MPS simulations.

Numerical Simulation of Particle Motion and Wall Scouring Behavior in Steelmaking Converter With Bottom Powder Injection

Numerical Simulation of Particle Motion and Wall Scouring Behavior in Steelmaking Converter With Bottom Powder Injection

A hybrid 1D-2D Lagrangian solver with moving coupling to simulate dam-break flow

In dam-break problems, two-dimensional (2D) models on the vertical plane appropriately capture the non-hydrostatic pressure distribution but with a high computational cost. This study presents a hybrid Lagrangian solver of one-dimensional (1D) shallow water flow and a 2D large-eddy simulation with a sub-particle scale to simulate dam-break flows over frictional beds. The proposed 1D-2D hybrid scheme is a useful trade-off between the accuracy of the 2D models on the vertical plane and the computational efficiency of 1D shallow water equations models. The configuration of sub-domains is established so that the 1D solves the regions with dominantly hydrostatic pressure, while the 2D solver accounts for the non-hydrostaticity. A moving coupling method is introduced based on two-layer shallow water equations with a uniform velocity distribution that constructs two sub-domains, including inner and outer zones in the section coupling model (SCM), or upper and lower layers within the layer coupling model (LCM). Then, the region with high vertical accelerations is substituted by the 2D model in the SCM or mixed SCM-LCM in which the overlapping zone and boundary interface move with time, based on the 1D flow feature. Also, a new method is proposed to deal with irregular boundary interfaces in the LCM while satisfying the momentum transfer. The present hybrid model is advantageous as it meets mass conservation, and there is no need for typical inflow/outflow boundary conditions at the coupling interfaces for simulating dam-break waves. Moving particle simulation (MPS) is utilized to solve the Lagrangian equations, which is advantageous in dealing with free-surface problems with large deformation. The model validation reveals that the hybrid results of water depths are in very good agreement with observed data and those obtained from the 2D model for selected dam-break flows with the ratio of initial depths downstream to upstream up to 0.4. In this respect, the average root-mean-square-error (RMSE) is computed at 8.09 mm in the SCM, 8.16 mm in the mixed SCM-LCM, and 7.48 mm in the pure 2D model, while both hybrid models save the computational time by 55% compared to the 2D model. Moreover, the mixed SCM-LCM preserves the nonlinearity of the wavefront over long times, whereas the SCM converts the wavefront into a shockwave considering the same number of fluid particles.

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.

Criticality Evaluation During Fuel Debris Particle Sedimentation Using Coupled DEM-MPS Code

From the viewpoint of criticality management in the fuel debris retrieval operation at the Fukushima Daiichi Nuclear Power Station, it is important in criticality safety analyses to consider the behavior of fuel debris particles as they fall into the water, given that the neutron moderation condition of the fuel debris can dramatically change. In this study, we evaluated a reactivity insertion while fuel debris particles dropped into the water. Specifically, we considered the effects of the fuel debris particle-size distribution in either an erroneous operation or a postulated accident in the fuel debris retrieval operation. Three types of fuel debris particle-size distribution were assumed: monodisperse, uniform, and Rosin-Rammler. The behaviors of the fuel debris particles during sedimentation were evaluated using the coupled Distinct Element Method–Moving Particle Simulation (DEM-MPS) code. The multiplication factors corresponding to the behaviors of the falling fuel debris were calculated by a continuous-energy Monte Carlo code MVP3.0 with JENDL-4.0. Consequently, the multiplication factors changed with the particle motions during the sedimentation, and the trends of the multiplication factors differed between the particle-size distributions. Especially, the 2-cm monodisperse particle-size distribution showed the highest multiplication factor during sedimentation, the trend of which differed from the others in the fuel debris particles dispersing and piled-up phases in the water.

Implementation of Lees–Edwards periodic boundary conditions for three-dimensional lattice Boltzmann simulation of particle dispersions under shear flow

In this research, the three-dimensional implementation of the Lees-Edwards boundary condition is presented and discussed for the simulation of particulate suspensions. The proposed method is based on the lattice Boltzmann and smoothed profile method for flow and particle motion simulation. This approach eliminates Galilean invariance errors when the particle crosses Lees–Edwards boundaries. Two important issues of particle crossing shear boundaries and corners of a computational domain are discussed in detail. Forces and torques evaluation for a particle that crosses boundaries need special treatment due to the division of the particle into two, four, and eight parts as it traverses one edge, and the intersection of two and three boundaries, respectively. The validation of the present method is performed by using some benchmarks. Furthermore, due to the ability of this algorithm to perform in parallel mode, a CUDA code based on the GPU platform is used to accelerate the computations. The results show that the parallel processing of this method on GPU significantly accelerates the computations.

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.

Newtonian and non-Newtonian food bolus behaviors obtained from validated swallowing simulator based on moving particle simulation

Newtonian and non-Newtonian food bolus behaviors obtained from validated swallowing simulator based on moving particle simulation

Morphology prediction of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) crystal in different solvent systems using modified attachment energy model

Effects of solvent, temperature, mixed solvent and its volume ratio on the morphology of TKX-50 crystal. (DMF: N , N -dimethylformamide; H 2 O: water; FA: formic acid; AcOH: acetic acid; EG: ethylene glycol). In order to theoretically study the growth morphology of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) crystal in different solvent systems, crystal–solvent models were established, and then molecular dynamics (MD) methods were adopted as a means to simulate particle motion. Modified attachment energy (MAE) model was employed to calculate the growth morphology of TKX-50. The simulation results demonstrate that COMPASS force field and RESP charge are suitable for molecular dynamics simulation of TKX-50. The morphologically dominant growth surfaces of TKX-50 in vacuum are (0 2 0), (0 1 1), (1 1 –1), (1 0 0) and (1 2 0), respectively. In water (H 2 O) and N , N -dimethylformamide (DMF) solvents, the (1 1 –1) face is the largest in the habit face, the growth rate of (0 2 0) face becomes faster. With the increase of temperature, the aspect ratios of TKX-50 crystal in DMF solvent increase, and the areas of the (1 2 0) faces decrease. In ethylene glycol / H 2 O mixed solvent system with volume ratio of 1 / 1, aspect ratio of TKX-50 is relatively small. In formic acid / H 2 O mixed solvents with different volume ratios (1 / 4, 1 / 3, 1 / 2, 1 / 1 and 2 / 1), aspect ratio of TKX-50 is relatively small when volume ratio is 1 / 2.

Numerical Simulations of Particle Motions at Continuous Rotational Speed Changes in Horizontal Rotating Drums

The motion of binary particles in three horizontal rotating drums with continuous rotational speed changes was studied based on the Discrete Element Method (DEM). Different simulation conditions were compared between two circular drums and an elliptical drum using the same number of physical properties for binary particles and drums, rotating at a speed series from 0.01 to 21.9 rad/s. By varying the rotational speed, four flow regimes were produced in the simulation. Flow regimes, velocity vectors, normal forces, and the number of contacts between 1 mm particles and 3 mm particles were comparatively analyzed, especially the particle velocity at transient changing rotational speeds. The results showed that four flow regimes were found at the same rotational speed for three different rotating drums, and normal forces were weakest for the cataracting regime; moreover, the three layers of particles were damaged when the rotational speed was suddenly decreased and the velocity direction of the particle motion was changed at the top of the particles’ bed. The maximum number of contacts was found with the rolling regime, based on the simulation results. The number of contacts of the major axis circular drum was smaller than for the minor axis at the same rotational speed, and the number of contacts of the elliptical drum was the largest among the three rotating drums.

An explicit particle method for simulation of multiphase flows

Weakly-compressible Moving particle simulation (WCMPS) is a Lagrange meshless method that is advantageous in solving complex fluid problems. Although the accuracy can be addressed in WCMPS, instability arises due to pressure fluctuations from particle clustering. Weakly Compressible Moving Particle Explicit (WCMPE) method improved the pressure calculation and stability of WCMPS while preserving its coding system with high computational efficiency. In this study, the multiphase WCMPE method is developed with a simple density smooth technique and interface detection procedure. Several numerical cases were investigated by the multiphase WCMPE method, including Rayleigh-Taylor (R-T) instability cases with various density and viscosity ratio conditions, oil spill and oil-water sloshing experiments. In general, good agreements with analytical solutions or from experimental data were obtained in multiphase WCMPE results with negligible unphysical pressure oscillation and pressure noise points.

An Oil Wear Particles Inline Optical Sensor Based on Motion Characteristics for Rotating Machines Condition Monitoring

Since inline monitoring method has the advantages of no sampling, being real-time, no human intervention, and low error, this paper innovatively proposes to study the inline monitoring of wear particles in an oil pipeline, from the perspective of the different motion characteristics of the particles. In this paper, an inline optical sensor was designed and developed by studying the velocity characteristics of different particles through theoretical calculations, numerical simulations, and experimental analysis. First, an equation for particle motion was statistically established, based on the forces acting on wear particles in an oil-filled vertical tube. Then a finite element model of particle motion in a full-flow oil pipeline was created, to simulate particle motion with various diameters, densities, locations, and shapes. Finally, the results of the theoretical study were effectively applied to design an inline optical monitoring sensor, and the experimental validation results demonstrated that the inline sensor has excellent suitability for monitoring wear particles. This study has significance for the safe operation of large rotating machinery.

Modelling Particle Motion during High-Voltage Electrostatic Abrasive Implantation Based on Multi-Physics Field Coupling

Electrostatic abrasive implantation technology is a classical process based on electrostatic field to implant abrasive particles into base material. However, there is still not a quantitative model to ensure the implantation performance due to the fact that the electrostatic abrasive implantation is a complex multi-physics coupled process. To ensure the quality of sandpaper and elucidate the complex motion mechanism of Al2O3 based abrasive particles in a high voltage electrostatic field, a multi-physical field coupling simulation model is proposed. First, the mechanical model is constructed for the complex problem of the electrostatic abrasive implantation process. Then, the field model is established for the problem that the superposition of multi-physical fields leads to complicated environmental conditions. Finally, the evaluation model is established for the problems that the abrasive planting effect is difficult to evaluate and the planting parameters are difficult to adjust. Besides, a tailored electrostatic abrasive planting testing equipment is designed for the implantation performance analysis purpose. Single-parameter electrostatic abrasive planting experiments were conducted to analyze and verify the effect of different pole plate voltage and pole plate spacing on the abrasive implantation rate. To ensure the implantation performance, the applicable pole plate spacing ranges from 30 mm to 50 mm and the suitable voltage is 20–40 kV according to the simulation result in the proposed two models. Meanwhile, the implantation rate experimentation shows the coupling field model coincides with the experiments better. The key factors affecting the electrostatic abrasive planting process are identified, and a feasible multi-physical field coupled abrasive particle motion simulation model is proposed.

Simulation of Particle Motion in a Two-Stage Mill

Simulation of Particle Motion in a Two-Stage Mill

Three‐dimensional weakly compressible moving particle simulation coupled with geometrically nonlinear shell for hydro‐elastic free‐surface flows

AbstractA three‐dimensional fluid–structure interaction solver based on an improved weakly compressible moving particle simulation (WC‐MPS) method and a geometrically nonlinear shell structural model is developed and applied to hydro‐elastic free‐surface flows. The fluid–structure coupling is performed by a polygon wall boundary model that can handle particles and finite elements of distinct sizes. In WC‐MPS, a tuning‐free diffusive term is introduced to the continuity equation to mitigate nonphysical pressure oscillations. Discrete divergence operators are derived and applied to the polygon wall boundary, of which the numerical stability is enhanced by a repulsive Lennard–Jones force. Additionally, an efficient technique to deal with the interaction between fluid particles placed at opposite sides of zero‐thickness walls is proposed. The geometrically nonlinear shell is modeled by an unstructured mesh of six‐node triangular elements. Finite rotations are considered with Rodrigues parameters and a hyperelastic constitutive model is adopted. Benchmark examples involving free‐surface flows and thin‐walled structures demonstrate that the proposed model is robust, numerically stable and offers more efficient computation by allowing mesh size larger than that of fluid particles.