Smoothed Particle Hydrodynamics Method Research Articles

Study on movement characteristics of snow-wind flow based on SPH method

Snowstorm disasters seriously endanger human life and the social economy. In order to find out the influence of the sublimation of snow on motion characteristic of snow-wind flow, based on Smoothed Particle Hydrodynamics (SPH), this paper simulates motion to propose the method and basic theory of the SPH model of snow-wind flow. The basic idea of the SPH method is to decompose the computational domain into independent particles. These computational particles carry their physical properties. And it can move with the governing equations, which is consistent with the discrete nature of snow particles. According to the advantages of the SPH method and the characteristics of snow flow, this paper improves and rectifies SPH theory, so that SPH shows its unique advantages in dealing with the coupling of two substances in the snow two-phase flow. This new model can able to achieving two functions: moisture diffusion and snow particle physical properties change with time and environment. And it can dynamically display the movement state of the salting snow particles of the whole snow-wind flow process to obtain each particle's speed, trajectory, and mass change. In this paper, the dynamic characteristics of snow particle swarm motion behavior are obtained through the microscopic analysis of a single snow particle motion physical quantity.

Numerical modelling of brittle fracture using lattice particle method with applications to fluid structure interaction problems via SPH coupling

This paper presents an improved failure model for simulating brittle fracture using the mesh-less Lattice Particle Method (LPM). By modelling the initial crack line using the Remove Bond (RB) approach as outlined in this paper, a new formulation is then developed for predicting the mode-I Stress Intensity Factor (SIF) near the crack tip. Compared to the conventional Remove Particle (RP) approach, it is found that the accuracy of the present SIF formulation based on the RB method is superior. A series of benchmark test cases are simulated to test the numerical accuracy and numerical convergence of the method. Finally, the LPM method is coupled with the Smoothed Particle Hydrodynamics (SPH) method for studying Fluid Structure Interaction (FSI) problems involving solid fracture and free surface. The coupled SPH-LPM method is implemented in the open-source code, DualSPHysics, which has been optimized for both CPU and GPU performances. Upon integrating LPM with SPH, the proposed FSI method is suitable for modelling fracture phenomena caused by natural hazards such as tsunami and flood.

Insights into the failure mode of the Chelyabinsk meteor from high-fidelity simulation

In 2013, an asteroid with a diameter of approximate 20 m broke up in the atmosphere above the Russian city of Chelyabinsk producing what is known as an airburst event. The event was recorded on video from multiple angles and a 500-kg fragment was recovered from Lake Chebarkul shortly thereafter. These aspects, coupled with the asteroid’s large size, distinguish the Chelyabinsk event as unique. In this study, we use the smoothed particle hydrodynamics method to examine the breakup mode of a Chelyabinsk-sized monolithic asteroid and probe whether a monolithic structure is consistent with observations from the Chelyabinsk event. We model the object as a homogeneous sphere with properties consistent with Chelyabinsk meteorites. We use planar-2D simulations to test the sensitivity of results to variations in the material model and to qualitatively inspect the cause of crack nucleation and fragmentation. We then compare results from a 3D simulation to observations from the event. Our 3D simulation predicts a burst height within 3 km of the observed peak luminosity suggesting the responsible asteroid may have been monolithic.

A strategy to introduce multi-gradient structures into iron by explosive shock wave processing

A strategy combining shock-induced phase transition, twins, and dislocations to produce a multi-gradient structure in Fe is designed and proposed by the explosive processing method. A specific emulsion explosive is designed to introduce gradient pressure into iron ranging from 8.3 to 13.4 GPa by smooth particle hydrodynamics method. The pressure range generated by explosive processing covered shock loading phase transition point, shock unloading phase transition point, twin activating point and elastoplastic dislocation point of iron, creating gradient phase transition, gradient twins, gradient dislocations and gradient grain size structures in iron. The mechanism of gradient grain size formation is illustrated based on the twins and dislocation boundaries. Due to the multi-gradient microstructure, a demonstrating gradient hardness range from 1231.3 Hv to 89.8 Hv is distributed from the surface to the internal of the iron. This method lays an experimental foundation for Fe, Ti, Mg based gradient materials that undergo phase transition under low shock pressure.

SPH approach for stability analysis of soil slope with variable permeabilities

A simulation framework based on meshless method has become an alternative numerical tool to model many deformation problems in geotechnical engineering. Large deformations in the failure zone can alter porosity, permeability etc., which in turn can affect the process of the failure. In this paper, a two-phase model in the framework of Smooth Particle Hydrodynamics (SPH) is introduced to model the interaction between water and soil through drag forces according to Darcy’s law. Changes in soil porosity and associated permeability are automatically adjusted within this framework. Firstly, two different problems i.e., flow through porous media and fluidized bed problem, are investigated to examine the suitability, and stability of the proposed SPH method. Then, the stability analysis of a soil slope under different water level conditions is performed with the strength reduction technique, and the groundwater effect of the slope is simulated. It is found that owing to the negative impact of seepage on soil slope, the horizontal displacement of the slope can be significantly larger. Afterwards, the influence of the variable permeabilities on the slope failure is investigated. The simulation results show that the change in permeability has a slight effect on the slope. Although the calculated safety factor does not change, the sliding distance differs by about 10%. The initial porosity has a large negative influence on the stability of the slope. The developed SPH model has been shown to be a valuable and effective tool for modelling complex problems that are challenging to be addressed with traditional approaches.

A Joint Johnson-Cook-TANH Constitutive Law for Modeling Saw-Tooth Chip Formation of Ti-6AL-4V Based on an Improved Smoothed Particle Hydrodynamics Method.

Titanium alloy is a crucial structural material in the modern aerospace field due to its strong corrosion resistance and strength, low density, and reduced sensitivity to vibration load and impact load, as well as its ability to resist expansion in the case of cracks. However, during high-speed cutting of titanium alloy, it is prone to periodic saw-tooth chip formation, which can cause high-frequency fluctuations in the cutting force, aggravate the vibration of the machine tool system, and ultimately reduce the tool's service life and the workpiece's surface quality. In this study, we investigated the influence of the material constitutive law in modeling the Ti-6AL-4V saw-tooth chip formation and proposed a joint material constitutive law JC-TANH which was developed based on the Johnson-Cook constitutive law and the TANH constitutive law. It has two advantages of the two models (JC law and TANH law), which means that it can describe the dynamic properties accurately, the same as the JC model, not only under low strain but also under high strain. The most important thing is that it does not need to fit the JC curve at the early stage of strain changes. Additionally, we established a developed cutting model, which integrates the new material constitutive, and the improved SPH method to predict chip morphology, cutting and thrust forces which are collected by the force sensor; we also compared the data with experimental results. Experimental results show that this developed cutting model can better explain the shear localized saw-tooth chip formation and correctly estimate its morphology as well as the cutting forces.

Interactive Simulation of Realistic Fluid Movement Based on SPH Method

With the continuous progress of computer simulation technology, fluid simulation has been developed rapidly, and it has beeen widely used in many fields, especially in engineering compution, game and special effects in movie. Nevertheless, with the increasing requirements of fidelity of the motion and interaction of subjects, fluid simulation requires more realistic simulation results. However, the motion of real fluid and objects is often difficult to be expressed by simple process, which can only be realized by the physical laws in the real world. Physical-based fluid simulation is one of the most challenging research issues due to its complexity in theory and computations. Among numerous fluid simulation models, Smoothed Particle Hydrodynamics (SPH) based fluid simution is the most widely used meshless method to simulate the realistic fluid motion. As a simple and flexible method, SPH partical characteristics make it naturally suitable for fluid simulation modeling and feasible to deal with many fluid simulation computation problems in a robust and stable way. The SPH basic principle, kernel function, discretization scheme and boundary treatments are introduced. The fluid movement is solved by SPH method in accordance with Navier-Stokes equations. The accuracy and stability of the fluid solution equation was improved by correcting the pressure and velocity fields. Secondly, the water surface was modeled and the rendering speed of the fluid surface was optimized by simplifying the fluid particles calculation. The SPH model is developed to simulate impulsive wave generated by dam-break and high speed landslide. It shows the model can simulate the movement process of the fluid fragment and coalescence, and available to simulate the blood, volcanic explosion and tsunami propagation.

A new smoothed particle hydrodynamics method based on high-order moving-least-square targeted essentially non-oscillatory scheme for compressible flows

In this study, we establish a hybrid high-order smoothed particle hydrodynamics (SPH) framework (MLS-TENO-SPH) for compressible flows with discontinuities, which is able to achieve genuine high-order convergence in smooth regions and also capture discontinuities well in non-smooth regions. The framework can be either fully Lagrangian, Eulerian or realizing arbitary-Lagrangian-Eulerian (ALE) feature enforcing the isotropic particle distribution in specific cases. In the proposed framework, the computational domain is divided into smooth regions and non-smooth regions, and these two regions are determined by a strong scale separation strategy in the targeted essentially non-oscillatory (TENO) scheme. In smooth regions, the moving-least-square (MLS) approximation is used for evaluating high-order derivative operator, which is able to realize genuine high-order construction; in non-smooth regions, the new TENO scheme based on Vila's framework with several new improvements will be deployed to capture discontinuities and high-wavenumber flow scales with low numerical dissipation. The present MLS-TENO-SPH method is validated with a set of challenging cases based on the Eulerian, Lagrangian or ALE framework. Numerical results demonstrate that the MLS-TENO-SPH method features lower numerical dissipation and higher efficiency than the conventional method, and can restore genuine high-order accuracy in smooth regions. Overall, the proposed framework serves as a new exploration in high-order SPH methods, which are potential for compressible flow simulations with shockwaves.

Numerical simulation research on fragments formation of cylindrical cased charge based on SPH method

In order to obtain the fracture and fragmentation of a cased charge under blast loading, the JWL equation of state of HMX-based PBX was fitted based on a cylinder test firstly, then the smooth particle hydrodynamics (SPH) method was used to perform a simulation of cased charge under interior blast loading, in the meantime, an blast test of cased charge was conducted. The results show that the parameters of JWL equation of state and the simulation method were reasonably. The simulated fragments velocities and calculated results from empirical formula agreed well with each other, the maximum error did not exceed 9.5%. Under the direct loading of the detonation wave, the fragments velocities increased to more than 1000m/s immediately within 5us, and then the fragments were continuously accelerated by detonation products and shock wave until the fragments reached the maximum velocities in the later 250us. Eventually, the shape of expansion contour of the casing tended to be ellipsoid. The method and results can provide references for the power design of the fragment warhead, as well as the protection design against the fragments.

Thermo-Structure Approach to Dissimilar Explosive Cladding with Interlayer

A thermodynamic model capable of predicting the change in internal energy, work done, and thermal energy required during aluminum-stainless steel explosive cladding is presented. The mathematical model is instrumental in determining the temperature and pressure developed at the interface, which characterizes the interface microstructure, compared with the numerical simulation. Numerical simulation is implemented by the Smoothed Particle Hydrodynamics method available in ANSYS Autodyn. Furthermore, the effect of different interlayers, such as Al 1100, copper, and SS 304, on kinetic energy utilization and deformation work is discussed. The increase in ram tensile and shear strengths is also reported.

Numerical analysis of water entry under ocean currents with smoothed particle hydrodynamics method

Water entry is a fluid–structure interaction process closely related to the ocean environment. Repeated water entries take place when ships are sailing in an ocean environment, e.g., ocean currents, which greatly affect the ship's safety and stability in navigation. In this paper, we adopt a smoothed particle hydrodynamics method to numerically study the water entry of a bow-flare ship body section under ocean currents. We simulate the process of water entry under different current velocities and analyze in detail the fluid field regarding the free surface evolution, the velocity and pressure distributions, and the body's forces and motions. It is revealed that the ocean current can induce multidirectional fluid impacts, and a stagnation point with zero velocity occurs at the upstream side. Asymmetric fluid fields including the evolution of the free surface and the velocity and pressure distributions around the body can also be found. In addition, discrepancies are caused in the formation time and the range of the high-pressure region. These fluid field changes greatly affect the ship body's dynamic responses. However, the effects of the ocean current are mainly reflected in the direction of the current flow and are relatively small in the direction perpendicular to the flow.

Bird strike simulation on a bonded Ti/CFRP leading edge of an engine fan blade

Bird strike represents a critical loading scenario for aeronautical structures, especially for engine fan blades. It is, therefore, of great importance both to protect the leading edge of the fan blade from impact damage and to be able to detect impact damage directly. In the present study, an explicit finite element (FE) model was developed using the LS-DYNA software to simulate bird strike on the leading edge of a CFRP fan blade protected by an adhesively bonded Ti layer. The model accounts for damage on the CFRP blade through a progressive damage modeling scheme and for debonding through a cohesive zone modeling scheme but not for damage on the Ti layer. For the modeling of the bird, the smooth particle hydrodynamics (SPH) method was used, due to the large deformations that were expected. Using the model, a parametric study on the effects of bird mass and impact energy was performed. The numerical results show that impact damage depends more on impact velocity than the bird mass. In all cases, debonding of the tip of the leading edge was predicted, while for combinations of small bird mass and large impact velocity a more extensive debonding of the protective layer was predicted. Regarding damage in the CFRP, only matrix cracking on the leading edge has been predicted. Aiming to assess the effectiveness of FBGs to detect debonding of the Ti layer due to bird strike, an FBG network has been modeled into the bondline and a study was performed on the correlation of the measured strains with impact damage.

Effect of ramming initial state on band engraving in smooth-bore guns

Most modern tank guns are high bore pressure smooth-bore guns that often use High Explosive Antiarmor (HEAA) projectile in combat. This paper focuses on the coupled smoothbore gun- HEAA projectile system, and analyses the projectile ramming-band engraving process when a tank fires HEAA projectile. First, a finite element mesh model of the coupling dynamics of a large-calibre tank gun smoothbore barrel and HEAA projectile was established, and the band was discretized by using the Smoothed Particle Hydrodynamics (SPH) method based on the Lagrange mesh. Then, the propellant gas pressure acting on the bore and the base of the projectile was defined by ABAQUS user’s subroutine. Finally, the ramming-engraving process simulations were carried out for the ramming residual stress and strain, ramming tilt and different ramming misalignment distances working conditions respectively. According to the simulation results, the effect of different ramming initial states on the band engraving process was obtained. The conclusion provides some reference for the simulation of the band engraving process.

Numerical investigation on the coupled vibrations of piezoelectric energy harvester with a liquid-filled proof mass

Replacing the solid tip mass of a piezoelectric cantilever beam with a liquid-filled mass can increase its frequency bandwidth due to the effect of nonlinear liquid sloshing. To investigate the coupled vibrations of the piezoelectric beam and the sloshing liquid, as well as their contributions to the output power, a coupled two-dimensional finite element method-smoothed particle hydrodynamics model has been developed in this study. Using this model, the dynamic behavior of a piezoelectric beam with a liquid-filled rectangular container as the tip mass, subjected to vertical harmonic excitation, has been investigated. The effects of parametric sloshing, excitation level, and geometric nonlinearity on the output voltages have been studied in detail. The simulation results indicate that: (a) the parametric sloshing in the liquid container exhibits subharmonic characteristics, which can be triggered by matching the excitation frequency to twice the natural frequency of the sloshing mode; (b) the piezoelectric beam exhibits subharmonic or harmonic oscillations at parametric resonance; (c) due to the effect of coupled vibrations, the energy harvester with a liquid-filled proof mass has a broader bandwidth compared to the traditional harvester; (d) the frequency response diagram of the output voltage shows multiple peaks at high excitation amplitudes, and the bifurcations are caused by parametric sloshing.

An energy stable incompressible SPH method with consistent solid boundary treatment

We propose two novel solid wall boundary treatments on the energy-stable Smoothed Particle Hydrodynamics (SPH) method for the Navier–Stokes system which models single-phase incompressible flows. In this work, the solid wall is discretized with dummy particles, and an external force is introduced to restrict the motion of solid particles, whose physical significance and numerical necessity are analyzed. We construct consistent fluid–solid coupling schemes based on the approaches so that the boundary condition is involved in the same equations system with particular constraints. Furthermore, the schemes are unconditionally energy-stable, which allows large time step sizes and leads to efficient computation. A variety of examples are demonstrated to verify the corresponding numerical analysis result, which shows that the approaches can easily handle no-slip and moving boundaries. Finally, we highlight that the energy-stable ISPH with consistent boundary treatments greatly benefits solving long-term problems with steady states.

FEM-SPH Coupling Approach for Impact Response Analysis of Composite Plates with Brick-and-Mortar Structure

Bioinspired nacre-like composites have attracted increasing research interests recently. They are typical composites with brick-and-mortar structure and usually employ a combination of hard material and soft material to achieve a good balance between stiffness and toughness. Impact response analysis of such composites is difficult due to their complex structure and interface. In this work, an effective finite element method-smoothed particle hydrodynamics (FEM-SPH) coupling approach is developed for impact response analysis of composite plates with brick-and-mortar structure. In the approach, hard material taking up the bulk of the composite plate is modeled with the SPH method, and soft material forming thin layer structures in the composite plate is modeled with FEM. A coupling algorithm considering failure behavior is proposed to model bonding interfaces between FEM parts and SPH parts. A particle-to-particle SPH contact algorithm is employed to handle contacts between SPH parts, and a penalty-based FEM-SPH contact algorithm is implemented to treat contacts between FEM parts and SPH parts. The developed coupling approach is used to calculate stress wave propagation in two bonded plates of the same material and different materials and a composite plate with brick-and-mortar structure. The accuracy of the coupling approach is validated by comparing the calculated results with those of analytical method and FEM. The coupling approach is then used to simulate the effects of some factors on the impact damage of composite plates with brick-and-mortar structure. The coupling approach can conveniently model the complex structure and bonding interface of the composite plates and is capable of capturing interface failure and fragmentation of the major composition of the composite plates during impact events. It provides a promising alternative for the impact response analysis of brick-and-mortar composite structures.

An improved SPH scheme for the 3D FEI (Fluid-Elastomer Interaction) problem of aircraft tire spray

The problem of aircraft tire spray produced by taking off or landing on wet runways is widely concerned. When simulating this kind of FEI(Fluid-Elastomer Interaction) problem with traditional SPH((Smoothed Particle Hydrodynamics) method, there are some drawbacks in both fluid and elastomer calculation. For the elastomer simulation, the TL-SPH(Total Lagrangian-SPH) is used to deal with the deformation of tire under complicated motion and load. For the fluid simulation, a new SPH scheme of Riemann solver combined with transport velocity is proposed to solve the problem of particle clumping when the free surface is suffering from violent splash. Then the tire spray model by unified SPH is established, in which both the tire deformation and the spray pattern are validated by experiments. Finally, based on the large-scale tire spray simulation, the phenomenon of tire hydroplaning is studied.

Using an improved SPH algorithm to simulate thermo-hydro-mechanical-damage coupling problems in rock masses

The Thermo-Hydro-Mechanical-Damage (THMD) process inside rock structures is a complex multi-field coupling problem, which is also regarded as the hotspot worldwide. In view of this situation, a fracture mark ξ is introduced to reflect the “active” or “failure” mode of Smoothed Particle Hydrodynamics (SPH) particles, which can simulate rock progressive cracking characteristics. The solid-water interaction modes and the damaged particles - water particles transformation algorithms are embedded into traditional SPH program to simulate the water-stress coupling problems. The heat conduction equations are programmed into SPH, which can reach the goal of modeling the temperature-stress coupling problems. Results show that: By coupling the parameter transformations between water and solid particles, the thermo-hydro-mechanical-damage simulation is then realized. Three numerical examples are carried out to validate the improved THMD method. Finally, an engineering numerical model of a typical tunnel is established, and the THMD coupling processes under complex conditions are simulated, which shows that the improved SPH method can simulate rock THMD multi-field coupling problems. The research results will help understanding the rock THMD coupling mechanisms, meanwhile, it can also promote the applications of SPH method into THMD modeling.

Influence of printing conditions on the extrudate shape and fiber orientation in extrusion deposition additive manufacturing

A numerical framework was developed in this study to investigate the influence of relevant Extrusion Deposition Additive Manufacturing (EDAM) processing conditions on the final fiber orientation, inter-bead void and cross-sectional geometry of the bead laid down as the extrudate. Specifically, four key processes of the EDAM process are studied, namely: (i) flow of 90° angle turn as the extrudate exits the nozzle and is laid down on the previous layer or the substrate, (ii) flow of the bead during compaction, (iii) flow of an extrudate deposited adjacent to the previously compacted bead, and (iv) flow of the adjacent bead during compaction. The simulations utilize an anisotropic viscous flow model implemented using the smoothed particle hydrodynamics method in Abaqus and fiber orientation vectors are evolved under the assumption of affine motion. The simulation results are compared with experiments for printed bead geometries produced and this comparison was shown to validate the modeling approach as useful for predicting fiber orientation, bead geometry, and bead-to-bead contact interface geometry. The processing parameters considered are nozzle height from the substrate, the ratio of the print speed to the extrusion speed (Vb/Ve), and the bead-to-bead lateral overlap distance. A series of virtual experiments were conducted, and the following observations were noted: (i) the bead printed with a high nozzle height has significantly more fiber alignment in the printing direction than the lower nozzle height, (ii) the ratio of the print speed and extrudate speed, Vb/Ve, of greater than unity results in greater fiber alignment than for Vb/Ve <1. The developed model illuminates the roles of process parameters in determining the microstructure of the printed bead and bead geometry.

Simulation of non-cohesive soil turning based on an SPH model

Soil turning is an infrastructure activity in the field of geotechnical engineering. In this study, we propose a new soil turning numerical model based on the Smoothed Particle Hydrodynamics (SPH) method, in which an elastoplastic constitutive model is implemented. To validate the model, firstly, a landslide benchmark test is studied, the error of the maximum sliding distance is only 1.5 % compared to the experimental data. Next, a combined experimental numerical investigation on the soil turning process is carried out. We compare the experimental observations with the numerical modeling results and find that the numerical error of the peak height and the horizontal distance of the soil is about 2.56 % and 3.37 %, respectively, indicating that the proposed SPH model can reproduce the soil turning process accurately. The simulation results also demonstrate that: (1) When the turning speed is increased, the turning resistance does not change significantly but leads to a more sufficient mixing of the soil; (2) There exists a critical turning angle above which the resistance increase significantly associates with a larger angle; (3) Increasing the burying depth of the tool helps to improve the mixing effect; however, leads to larger resistance as well.