Smoothed Particle Hydrodynamics Model Research Articles

Modeling of machining of EB-PVD ceramic coatings using smoothed particle hydrodynamics method

In this work, an improved Smoothed Particle Hydrodynamics (SPH) based model for simulating the machining process of the thermal barrier coatings is presented. The columnar grain microstructure in the electron-beam physical vapor deposition (EB-PVD) coating is constructed. The Johnson-Holmquist 2 (JH-2) material model coupled with the Johnson-Holmquist plasticity damage model is used for the ceramic coating. The model validation is conducted by the comparison between the SPH model and qualitative agreement with experimental observation, and a quantitative agreement with the one-dimensional stress wave analytical model. In the SPH model, the cutting processing parameters, such as cutting depth, cutting speed, cutting tool's edge radius, rake angle on the cutting force, and temperature change are studied. The results show that the fracture of the columnar grains during the cutting process is done through deflection and fracture of the grains, followed by pushing against neighboring grains. Both the cutting force and temperature of the coating increase with cutting depth due to increased cutting work which is transferred to heat. The cutting forces from the SPH model at the stable stage are in excellent agreement with the fracture mechanics analytical solution. The cutting force and temperature increase are higher for a larger edge radius, due to increased friction between the cutting tool and coating. The SPH model result follows the same trend as the main cutting force calculated by the analytical expression. The SPH cutting model developed in this work can be used as a design tool to optimize the coating machining process.

Study of the Influence of Cutting Edge on Micro Cutting of Hardened Steel Using FE and SPH Modeling.

Micromachining allows the production of micro-components with complex geometries in various materials. However, it presents several scientific issues due to scale reduction compared to conventional machining. These issues are called size effects. At this level, micromachining experiments raise technical difficulties and significant costs. In this context, numerical modeling is widely used in order to study these different size effects. This article presents four different numerical models of micro-cutting of hardened steel, a Smooth Particle Hydrodynamics (SPH) model and three finite element (FE) models using three different formulations: Lagrangian, Arbitrary Eulerian–Lagrangian (ALE) and Coupled Eulerian–Lagrangian (CEL). The objective is to study the effect of tool edge radius on the micro-cutting process through the evolution of cutting forces, chip morphology and stress distribution in different areas and to compare the relevance of the different models. First, results obtained from two models using FE (Lagrangian) and SPH method were compared with experimental data obtained in previous work. It shows that the different numerical methods are relevant for studying geometrical size effects because cutting force and stress distribution correlate with experimental data. However, they present limits due to the calculation approaches. For a second time, this paper presents a comparison between the four different numerical models cited previously in order to choose which method of modeling can present the micro-cutting process.

SPH modelling of the water nappe gravity fall over a dam

This work uses the smoothed particle hydrodynamics (SPH) meshless numerical method in order to investigate the behaviour of a water sheet falling under gravity by reproducing the experimental results of a laboratory chute of 9.5 m height. This kind of flow occurs typically over dam ogee-type spillways. The focus is on the trajectory and velocity of the water sheet as well as on the pressure upon impact. Simulations using a combination of adaptive particle refinement, surface tension model and air friction model were tested. The SPH simulations with refinement show good agreement with the experimental pressure results for all comparisons, while using air friction allows correct modelling of the falling velocity distribution.

Experimental and Numerical Investigation of Floating Large Woody Debris Impact on a Masonry Arch Bridge

Masonry arch bridges form an essential part of existing transport infrastructure around the world, including mainland Europe and the northeastern US. Recent extreme flood events highlight that masonry arch bridges spanning watercourses are vulnerable to flood-induced hydrodynamic and debris impact loads. When the flow interacts with the bridge superstructure, with or without discrete floating debris, a complex interaction is observed. This paper presents both experimental and numerical studies to investigate this complex phenomenon, including fluid–structure and structure–structure interactions. A typical single-span masonry arch bridge and large woody debris representing a tree log are investigated. Experimental observations from a scaled hydraulic model, with and without debris in the flow, are first presented for the case where the abutment of the bridge is fully submerged. Next, the capability of the numerical method smoothed particle hydrodynamics (SPH) in simulating the hydrodynamic behaviour and debris impact observed in the experiment is discussed. Following this, both hydrodynamic and debris-induced pressure–time histories on the bridge are obtained using the SPH model. Results reveal that the debris impact leads to a significantly more localised load on the bridge compared to the situation with hydrodynamic load only.

Modeling the effect of backfill on dynamic fracture propagation in steel pipelines

In this paper, dynamic ductile fracture propagation simulations were conducted to study the use of smoothed particle hydrodynamics (SPH) for modeling the effects of backfill in pipeline burst simulations. The effect of SPH parameters on fracture velocity was studied using the Battelle Two-Curve Method (BTCM) approach of decoupling mechanics and gas decompression but characterizing propagation toughness by crack tip opening angle (CTOA) rather than Charpy absorbed energy (CVN). The backfilled pipe model was developed and studied using the commercial finite element code ABAQUS 2017. Ductile fracture propagation was simulated using a shell based constant CTOA model. The current study examined the numerical aspects of applying SPH through comparing results with literature. The effects of particle size, various backfill material properties, and backfill depth on the fracture velocity were examined. It was found that the particle size had a minor effect on the fracture velocity and should be selected in proportion to the diameter of the pipe being examined. The numerical study showed that increasing the density and shear modulus of the backfill material resulted in a reduction of the fracture velocity. The effect of backfill depth up to 1.4 m was also examined numerically and found to have little effect on the fracture velocity, agreeing well with literature. The present study illustrates the sensitivity of the fracture velocity to the various parameters used in SPH models.

3D multi-resolution SPH modeling of the water entry dynamics of free-fall lifeboats

Lifeboats can be launched through free-fall in extreme maritime accidents to fast leave the hazardous area, which deserves particular attention because it is tightly related to the safety of lifeboats and the carried passengers as well. This paper, within the framework of a fully 3D and multi-resolution Smoothed Particle Hydrodynamics (SPH) model, aims at investigating the water entry dynamics of a free-fall lifeboat with different water entry angles. First of all, two rigorous model validations are performed to demonstrate the accuracy, stability and convergence of the present SPH model. Furthermore, the water entry dynamics of the lifeboat with respect to different water entry angles, including the motion characteristics and cavity evolutions, is investigated and discussed in detail based on the SPH results. It is clearly demonstrated that the present SPH model possesses (1) satisfactory accuracy for predicting the water entry dynamics of a lifeboat, and (2) a better ability to capture the splashing jets and scattering droplets than mesh-based solvers thanks to its entirely Lagrangian nature. In addition, it is also demonstrated that the water entry angle exerts significant effects on the water entry dynamics of a lifeboat, which should be taken into account in the design stage to provide safer productions.

Application of SPH method in the study of ship capsizing induced by large-scale rising bubble

In some sea areas, the rising storm of bubbles including the release of large-scale methane gas and eruption of submarine volcanoes will pose a potential threat to the safety of ships. In the former case, a large amount of rising methane gas may generate some large-scale bubbles which may cause sailing ships to capsize. When the size of the bubble is close to the characteristic length of the ship, one single bubble could sink a ship. For the latter, the initial radii of the bubbles formed by the eruption of shallow seafloor volcanoes maybe tens even hundreds of meters, which also largely increases the risk of maritime transportation. In this paper, a 2D smoothed particle hydrodynamics (SPH) model is used to investigate the interaction between a ship and large-scale bubbles. Firstly, the adopted SPH model is validated by comparing with other numerical results. Then, the coupling interaction between a bubble and free-surface is simulated. Finally, under different conditions of different bubble sizes, bubble depths and horizontal distances, interactions between a ship and one or two large-scale rising bubbles are simulated and discussed, aiming to provide a reference for the investigation of ship capsizing caused by large-scale rising bubbles.

An Analysis of the Effect of Abrasive/Tool Wear on the Ductile Machining of Fused Silica from the Perspective of Stress.

Understanding the influence mechanism of abrasive/tool wear on machining is the key to realize high-efficiency ultra-precision machining of fused silica. To explore the effect of abrasive/tool wear on ductile machining, the smoothed particle hydrodynamics (SPH) cutting models with different edge radii are established. Through the analysis of equivalent rake angle, hydrostatic pressure, cutting force and maximum principal stress with the Flamant’s formula, the influence of edge radii on ductile-brittle transition (DBT) is discussed for the first time. The simulation results show that when the edge radius increases from less to larger than the cutting depth, the equivalent rake angle changes from positive to negative, and the maximum hydrostatic pressure gradually increases, which is beneficial to promote the ductile processing. Meanwhile, with the rise of edge radius (i.e., abrasive/tool wear), both the cutting force and crack initiation angle increase, while the friction coefficient and normalized maximum principal decrease. When the value of normalized maximum principal stress exceeds 2.702, the crack in the workpiece begins to initiate, and its initiation angle calculated by the Flamant’s formula is in good agreement with the simulation results as well as less than 50°. Finally, the nano-scratch experiment was carried out, and the material removal mechanism and friction coefficient f similar to the simulation were obtained, which further proved the accuracy of SPH model. This study is meaningful for understanding the effect of abrasive/tool wear on the removal mechanism of brittle materials and improving the quality and efficiency of cutting and grinding.

Experimental and numerical study on micro-blasting process of 3A dental implant titanium alloy: A comparison between finite element method and smoothed particle hydrodynamics

In the present study, solid particle erosion due to micro-blasting of dental implants (3A) made of titanium alloy under the impact of multiple alumina particles with an average diameter of 85 μm was analyzed, experimentally and numerically. The numerical investigation was conducted using finite element (FE) and smoothed particle hydrodynamics (SPH) methods. The erosive behavior of this alloy was simulated as impacts in micro-scale based on Johnson-Cook constitutive equations. By focusing on the particles impacts, a representative volume element (RVE) technique was proposed to simulate the arbitrary multiple particle impacts. The results of FE and SPH models are validated and compared with the experimental results. The effects of particle velocity and impact angle on the erosion rate of the alloy are then investigated. Finally, an equation is presented for prediction of the erosion rate versus velocity and angle of impact. The results indicate that for all impact velocities, the combination of penetration and cutting can create a critical condition of erosion damage for the titanium alloy.

Towards Depth-Averaged Modelling of the Decay of Granular Flows by Deposition

Depth-averaged (DA) numerical models are often used to simulate the runout of flow-type landslides because of their practicality and computational efficiency. However, existing DA models generally overlook the effects of deposition, which governs the decay of the flow momentum and the runout distance. In this study, a new approach is proposed to model the effects of deposition. The flow-normal accelerations that drive the deposition process are simulated using a high-fidelity two-dimensional (2D) Smoothed Particle Hydrodynamics (SPH) model. Based on the 2D non-DA SPH results, a deposition model that considers the initial aspect ratio (i.e., height to length) of the debris and slope angle is developed and implemented into the DA context to provide a practical tool for engineering simulations. The new DA SPH model is evaluated against experimental results in the literature. By considering the effects of deposition, predictions of the runout and flow duration are improved by up to 38%. The new DA SPH model works particularly well for runout predictions of large initial aspect ratios of the debris, which has traditionally been the limitation of DA models. The new framework can be used to advance towards realistic deposition and entrainment modelling to improve the delineation of flow-type landslides in mountainous regions.

Study of the weakly-compressible SPH method for improving pressure distribution of violent fluid-structure impact flows

Abstract When a traditional Weakly-Compressible Smoothed Particle Hydrodynamics (WCSPH) model is used to simulate free surface flow with a large Reynolds number, an unstable numerical calculation due to high random pressure oscillations will result, while an accurate pressure field is of vital significance for simulating violent fluid-structure interactions. Riemann-based SPH and Delta-SPH are widely used to solve this problem. In this paper, to enhance computational efficiency, the SPH method is implemented on a General Processing Unit (GPU) platform using Compute Unified Device Architecture (CUDA). Parallelized SPH programs including the standard SPH method, Riemann-based SPH and Delta-SPH are verified by a dam break model with large Reynolds number and violent deformation of free surfaces. The results show that all SPH methods can vividly reflect the whole process of splashing, rolling and backward jet flow; both the Riemann-based SPH and the Delta-SPH methods are effective in alleviating the problem of inhomogeneous pressure distribution in the simulation process; the Riemann-based SPH method has better stability even with relatively large particle spacing, and it has higher accuracy in simulating impact pressure. When the number of particles reaches 100,000, compared with a single-thread Central Processing Unit (CPU) implementation, the speedups obtained with NVIDIA Titan V with high computing cores and Quadro K2200 with low computing cores are thousands and hundreds, respectively.

Investigation on the bouncing and coalescence behaviors of bubble pairs based on an improved APR-SPH method

Bubbles rising in fluids are widespread in many engineering fields. In this paper, the bouncing and coalescing of two bubbles rising side by side are studied based on a multi-phase smoothed particle hydrodynamics (SPH) model. An improved adaptive particle refinement (APR) scheme is applied in the SPH model to make the numerical simulation sufficiently accurate and efficient. The effect of the surface-tension model is firstly verified, then various testing cases including the rising of a single bubble and two horizontally positioned bubbles are carried out and validate the numerical model well. Furthermore, the interaction between two three-dimensional bubbles rising side by side is studied considering the effects of viscous forces (with the Reynolds number Re), surface tensions (with the Eotvos number Eo), and the initial centroid distance of the two bubbles (Γ). The motion and the deformation of the bubbles are displayed and the mechanism of the bubbles' interaction is discussed. The results reveal that for the lower Eotvos number cases indicating a larger surface tension effect, the surface tension force increases dramatically when the two bubbles collide with each other and coalesce.

Study on physical behaviors according to element formulations of ballistic impact simulation models

During modeling ballistic impact, physical behaviors were investigated according to element formulations. In order to conduct the investigation, a simple ballistic impact simulation model was used. Several case studies consisting of FEM (Finite Element Method) and SPH (Smoothed Particle Hydrodynamics) models were conducted using the LS-DYNA research/commercial code. As a result, these case studies suggest that the SPH formulation is effective to simulate interactions among particles after failures so that the penetration phenomenon of the projectile were well described. In addition, some parameters relating to the SPH formulation such as particle spacing and smoothing length constant were investigated. Finally, for the verification, 20 mm fragment simulating projectile tests to verify the protection performance of K9 Thunder grill louver were compared with the simulations applying the FEM and SPH formulations.

Numerical Simulation of Orthogonal Machining of Gallium Nitride via Smoothed Particle Hydrodynamics

Gallium Nitride is one of the best candidates for upcoming industrial revolution due to itssuperior electrical properties over silicon. In the present work, we investigate the chipformation, cutting force and effective stress in diamond machining of gallium nitride bysmoothed particle hydrodynamics approach based on Mohr-Coulomb material model. Thecomparison of the effective stress as reported by molecular dynamics studies and thatpredicted by the smoothed particle hydrodynamics simulation demonstrates the effectivenessof the smoothed particle hydrodynamics model.

Numerical investigations on bionic propulsion problems using the multi-resolution Delta-plus SPH model

The bionic propulsion has garnered increasing attention in both scientific and industrial communities of underwater bionic vehicles on account of its higher efficiency, less noise, and remarkable self-shelter capability. This paper is dedicated to investigating the propulsion mechanism of fish swimming using the Smoothed Particle Hydrodynamics (SPH) method. Two fish-like swimming problems, established with rigid flapping foils and deformable anguilliform swimmers respectively, are simulated using the δ+-SPH model under the laminar flow assumption. First of all, numerical benchmarks are implemented to validate the convergence and accuracy of the SPH model by comparing the SPH results with experimental data quantitatively and qualitatively. Furthermore, the mechanisms of the thrust generation of the bionic swimmers are investigated and discussed in detail from the viewpoint of vortex shedding patterns and several dimensionless parameters describing the motion characteristics. It is demonstrated that the thrust force is tightly related to the shape and scale of the vortex shedding in wakes, and that a higher Reynolds number or larger Strouhal number, as well as a larger motion amplitude, are in favor of improving the thrust. In addition, the numerical results also indicate that the SPH method possesses great potential for the simulation of bionic propulsion problems thanks to its Lagrangian and meshfree nature.

Modelling cell deformations in bioprinting process using a multicompartment-smooth particle hydrodynamics approach.

Bioprinting using cell-laden bioink is a rapidly emerging additive manufacturing method to fabricate engineered tissue constructs and in vitro models of disease biology. Amongst different bioprinting modalities, extrusion-based bioprinting is the most conveniently adopted technique due to its affordability. Bioinks consisting of living cells are suspended in hydrogels and extruded through syringe-needle assemblies, which subsequently undergo gelation at the collector plate. During the process, pressure is exerted on living cells which may cause cell deaths. Thus, for selected combination of cell and hydrogel, exerted pressure and the extrusion play key roles in determining the cell viability. Experimental evaluation to characterise stresses experienced by the cells in a bioink during bioprinting is a tedious exercise. Herein, computational modelling can be applied efficiently for rapid screening of bioinks. In the present study, a smoothed particle hydrodynamics model is developed for the analysis of stresses exerted on the cells during bioprinting process. Cells are modelled by assigning different mechanical properties to nucleus, cytoskeleton and cell membrane regions of the cell to get a more realistic understanding of cell deformation. The cytoplasm and nucleus are modelled as finite element meshes and a spring model of the cell membrane is coupled to the finite element model to develop a three-compartment model of the cell. Cell deformation is taken as a potential indicator of cell death. Effect of different process parameters such as flow rate, syringe-nozzle geometry and cell density are investigated. A submodeling approach is further introduced to predict deformation with higher resolution in a unit volume containing 104 to 108 cells. Results suggest that the generated bioink flow dynamic model can be a useful tool for the computational study of fluid flow involving cell suspensions during a bioprinting process.

Coupled Electrohydrodynamic and Thermocapillary Instability of Multi-Phase Flows Using an Incompressible Smoothed Particle Hydrodynamics Method

This paper concerns the study of coupled effects of electrohydrodynamic (EHD) and thermocapillary (TC) on the dynamic behaviour of a single liquid droplet. An incompressible Smoothed Particle Hydrodynamic (ISPH) multiphase model is used to simulate EHD-TC driven flows. The complex hydrodynamic interactions are modeled using the continuum surface force (CSF) method, in which the gradient of the interfacial tension and the Marangoni forces are calculated with an approximated error or 0.014% in the calculation of Marangoni force compared to the analytical solutions which is a significant improvement in comparison with previous SPH simulation studies, under the assumption that the thermocapillarity generates sufficiently large stress to allow droplet migration, while the electrohydrodynamic phenomena influences the droplet morphology depending on the electrical and thermal ratios of the droplet and the ambient fluid. This study shows that, when applying a vertical electric field and thermal gradient, the droplet starts to stretch horizontally towards a break-up condition at a high rate of electrical permitivity. The combined effect of thermal gradient and electric field tends to push further the droplet towards the break-up regime. When the thermal gradient and the electric field vector are orthogonal, results show that the droplet deformation would take place more slowly and the Marangoni forces cause the droplet to migrate, while the stretching in the direction of the electric field is not seen to be as strong as in the first case.

Quantitative evaluation of SPH in TIG spot welding

While the application of the Smoothed Particle Hydrodynamics (SPH) method for the modeling of welding processes has become increasingly popular in recent years, little is yet known about the quantitative predictive capability of this method. We propose a novel SPH model for the simulation of the tungsten inert gas (TIG) spot welding process and conduct a thorough comparison between our SPH implementation and two finite element method (FEM)-based models. In order to be able to quantitatively compare the results of our SPH simulation method with grid-based methods, we additionally propose an improved particle to grid interpolation method based on linear least-squares with an optional hole-filling pass which accounts for missing particles. We show that SPH is able to yield excellent results, especially given the observed deviations between the investigated FEM methods and as such, we validate the accuracy of the method for an industrially relevant engineering application.

Characteristics of iceberg calving-generated waves based on three-dimensional SPH simulations

Large-scale icebergs calving into water often generate waves that may threaten human lives or passing ships. The formation and evolution of such three-dimensional (3D) waves in the near field are still not fully understood. In this paper, a 3D numerical model based on the Smoothed Particle Hydrodynamics (SPH) open source code DualSPHysics was established to simulate the generation and evolution processes of waves caused by icebergs calving into water. The model is validated with available large-scale laboratory tests. The 3D characteristics in the near field of the waves are presented and analyzed in detail. The results indicate that iceberg calving can generate three main waves: a leading wave produced by the initial entry of the iceberg into the water; a second wave induced by the collapse of the water jet; and a third wave caused by the resurfacing of the iceberg. The reflux tail blocked by the reflux front may appear prior to the second wave, which can develop into a constantly changing wavefront, and then form a step-like flow structure in the near field by linking these two wavefronts. The shapes of the multiple wavefronts outlined by the leading wave and the trailing waves in the near field are closely related to the iceberg geometry. However, the wavefronts gradually develop into a semicircular shape in the far field irrespective of the iceberg geometry. These findings are helpful for hazard assessments of iceberg calving-generated waves. • A rigid body–fluid coupled SPH model is established to simulate three-dimensional iceberg calving-generated waves (ICGW). • The three-dimensional characteristics of ICGWs in the near field are presented. • ICGW consists of three main waves: a leading wave; a second wave by water jet; and a third wave by resurfacing. • The generation and evolution processes of the multiple wavefronts are outlined.

An Effective Smoothing Length Updating Method for Smoothed Particle Hydrodynamics

Smoothing length plays a significant role in smoothed particle hydrodynamics (SPH). Inappropriate smoothing length will result in problems of stability, accuracy and efficiency. Updating smoothing length with time is very important for SPH modeling of large deformation problems. In this work, an effective smoothing length updating method is proposed. The method works in the framework of SPH with scalar smoothing length. It is quite simple in implementation and is computationally efficient. The method updates smoothing length according to maximum local particle spacing and inhomogeneity of material deformation. Numerical examples in both 2D and 3D which involve large deformation are calculated to validate the effectiveness of the proposed method. A comparison between the proposed method and several traditional methods is performed. Numerical results show that the present method can adapt to the simulation of severely inhomogeneous deformation and produce better stability and accuracy than the traditional methods for SPH modeling of large deformation problems.