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The vertical distribution of debris flow profile velocity is the key to studying debris flow, impulse and the sediment carrying process. At present, the linear distribution model based on flume test results cannot describe the vertical distribution of debris flow velocity effectively due to the limitation of measurement methods. In this paper, the smooth particle hydrodynamics (SPH) numerical model based on the Herschel–Bulkley–Papanastasiou (HBP) constitutive model is utilized to invert the three-dimensional dynamic process of debris flow based on a large-scale debris flow flume experiment. With a hierarchical statistical approach, a huge number of particle velocity data were analyzed and processed to obtain the vertical distribution law of velocity. We proposed a nonlinear vertical distribution model of debris flow velocity based on logarithm function accordingly. We also applied the proposed model to the existing debris flow entrainment estimation framework. A flume dam break test case was inverted to verify the performance of erosion calculations. The results show that the numerical simulation results of erosion depth are close to the experimental values. The error percentage of maximum erosion depth is 4.1%. The average error percentage of erosion depth simulation results is 15.5%. [ABSTRACT FROM AUTHOR]

Entrainment of saturated bed material increases the mobility of fast landslides. The distribution of excess pore pressures changes in the body of the landslide, as the material entering it has much lower effective confining stresses which results on much smaller apparent basal friction angles. The purpose of this paper is to enhance the Finite Differences depth integrated SPH model developed by the authors to cope with material which is flowing up the FD meshes. The model is set within an Arbitrary Lagrangian Eulerian framework (ALE), and the resulting excess pore pressure evolution model will include now advective terms in addition to the diffusive and source terms. In order to assess the importance of the proposed modification, we introduce a basal Péclet number which relates two non dimensional reference times of consolidation and erosion. [ABSTRACT FROM AUTHOR]

Interlayer plays an important role in improving the welding quality of explosive welding. In this study, four different welding interfaces were subjected interlayer explosive welding to demonstrate advantages of interlayer explosive welding over direct welding. The results indicated that using an interlayer in explosive welding could reduce excessive melting, enlarge the weldability window, reduce the vortex region, and reduce the large plastic deformation between interfaces. Smoothed particle hydrodynamics (SPH) simulations were used to simulate the different welding processes, which provided information on the interface morphology, temperature, melting, and pressure. The simulated results were found to correlated very well with the experimental results. [ABSTRACT FROM AUTHOR]

Storage basins, check dams, barriers and other control works are often used to reduce threats and damage from flow-like mass movements. This paper deals with the effectiveness of two storage basins of the Italian Alps against debris flows followed by a flash flood induced by short heavy rainfall in 2009. Referring to detailed field data, the propagation of flows and their interaction with the control works are analysed by using an advanced numerical depth-averaged flow propagation model based on SPH (Smooth Particle Hydrodynamics) technique. The Froude dynamic similitude is here used to provide a quantitative descriptor of the dynamic features of the flows. The numerical results show that debris flows accumulated in the storage basins since they propagated downslope like subcritical flows. On the contrary, flash floods overpassed the control works having moved along the entire path as supercritical flows. Those findings are fully supported by some previous studies and provide a further contribution to the relevant topic of granular flow-obstacle interaction. [ABSTRACT FROM AUTHOR]

The paper presents an analysis of applicability of two meshless methods for pistol bullets modelling based on an example of a 9 mm Parabellum. The studies included the following methods: Smoothed Particle Hydrodynamics (SPH) method and Smoothed Particle Galerkin (SPG) method. The results of computer simulations were confronted with ballistic test results in terms of shapedimensional compliance of the deformed projectile. The relative error of the projectile diameter was 15% and 17% for the SPG and SPH methods, respectively. The deformation form for the SPH method deviated from the ballistic test results, while the SPG method faithfully reproduced the shape of the deformed projectile. Keywords: mechanical engineering, impact simulation, pistol bullet, SPH, SPG

Abstract The water entry is a classic fluid-structure interaction problem in ocean engineering. The prediction of impact loads on structure during the water entry is critical to some engineering applications. In this paper, a multiphase Riemann-SPH model is developed to investigate water entry problems. In this model, a special treatment, a cut-off value for the particle density, is arranged to avoid the occurrence of negative pressure. A remarkable advantage of the present multiphase SPH model is that the real speed of sound in air can be allowed when simulating water-air flows. In the present work, considering the air effect, several typical water entry problems are studied, and the evolution of multiphase interface, the motion characteristic of structure and complex fluid-structure interactions during the water entry are analyzed. Compared with the experimental data, the present multiphase SPH model can obtain satisfactory results, and it can be considered as a reliable tool in reproducing some fluid-structure interaction problems.

Background: In the smoothed particle hydrodynamics (SPH) fluid simulation method, thesmoothing length affects not only the process of neighbor search but also the calculation accuracy of the pressure solver. Therefore, it plays a crucial role in ensuring the accuracy and stability of SPH. Methods: In this study, an adaptive SPH fluid simulation method with a variable smoothing length is designed. In this method, the smoothing length is adaptively adjusted according to the ratio of the particle density to the weighted average of the density of the neighboring particles. Additionally, a neighbor search scheme and kernel function scheme are designed to solve the asymmetry problems caused by the variable smoothing length. Results: The simulation efficiency of the proposed algorithm is comparable to that of some classical methods, and the variance of the number of neighboring particles is reduced. Thus, the visual effect is more similar to the corresponding physical reality. Conclusions: The precision of the interpolation calculation performed in the SPH algorithm is improved using the adaptive-smoothing length scheme; thus, the stability of the algorithm is enhanced, and a larger timestep is possible.

Background: SPH method has been widely used in the simulation of water scenes. As a numerical method of partial differential equations, SPH can easily deal with the distorted and complex boundary. In addition, the implementation of SPH is relatively simple, and the results are stable and not easy to diverge. However, SPH method also has its own limitations. In order to further improve the performance of SPH method and expand its application scope, a series of key and difficult problems restricting the development of SPH need to be improved. Methods: In this paper, we introduce the idea of Helmholtz decomposition into the framework of smoothed particle hydrodynamics (SPH) and propose a novel velocity projection scheme for three-dimensional water simulation. First, we apply Helmholtz decomposition to a three-dimensional velocity field and decompose it into three orthogonal subspaces. Then, our method combines the idea of spatial derivatives in SPH to obtain a discrete Poisson velocity equation. Finally, the conjugate gradient (CG) is utilized to efficiently solve the Poisson equation. Results: The experimental results show that the proposed scheme is suitable for various situations and has higher efficiency than the current SPH projection scheme. Conclusion: Compared with the previous projection scheme, our solution does not need to modify the particle velocity indirectly by pressure projection, but directly by velocity field projection. The new scheme can be well integrated into the existing SPH framework, and can be applied to the interaction of water with static and dynamic obstacles, even for viscous fluid.

Total Lagrangian Smoothed Particle Hydrodynamics (TLSPH) is one variant of SPH where the variables are described using the fixed reference configuration and a Lagrangian smoothing kernel. TLSPH elevates the computational efficiency of the standard SPH when no topological change is involved, and it alleviates the stability of SPH scheme with respect to tensile loading. However, instabilities associated with spurious mode, or hourglass/zero-energy mode, persists and often affects the simulation of solids undergoing extremely large strain. This work proposes an alternative formulation to compute deformation gradient with improved accuracy and therefore minimising the possibility of encountering the zero-energy mode. Specifically, we leverage the local discrete computation of bond-based (or pairwise) deformation gradient smoothed by the kernel. Additionally, the bond of a particle with itself is considered to preserve the polynomial reproducibility imposed by the kernel correction scheme. We showcase the convergence of the approach using a two-dimensional benchmark example. Furthermore, the accuracy, robustness, and stability of the proposed approach are assessed in various two- and three-dimensional examples, highlighting on the stability improvement that allows for solid dynamic simulations with more extreme elongation. • An alternative formulation for calculating deformation gradient to improve accuracy. • The proposed method achieves an optimum convergence rate. • Stability improvement to reduce the risk of encountering the zero-energy mode. • Application for nonlinear solid dynamics with extreme elongation and large strain. [ABSTRACT FROM AUTHOR]

Coastal vegetation serves as an effective nature-based solution for protecting shorelines from erosion and storm surges. A detailed understanding of the dynamic interactions between waves and vegetation is crucial for quantifying the mitigation potential of coastal vegetation during extreme climatic events. This study investigates wave dynamic interactions with coastal vegetation by developing a numerical model using the weakly compressible Smoothed Particle Hydrodynamics (WCSPH) method. The model simulates the effects of vegetation by incorporating vegetation porosity, drag, and inertia forces into the momentum equations. By integrating porosity information at specific background points, the SPH interpolation method effectively treats the interfaces between fluid and vegetation regions, allowing versatility in modeling various vegetation layouts without explicitly simulating their solid structures, which is computationally prohibitive. The numerical model is validated using laboratory-based measurements and analytical models for both submerged and emergent scenarios involving cylindrical and strip-type vegetation. The model is then utilized to investigate the effects of vegetation as both a natural line of defense and a retrofitting solution in front of a sea dike, to quantify the performance of nature-based solutions for enhancing climate resilience in natural and hybrid coastal protection infrastructures. The results reveal that canopy density significantly impacts solitary wave run-up and energy dissipation. For the configurations tested in this study, high-density vegetation reduces normalized wave run-up by 52% compared to simulations without vegetation, while low-density vegetation achieves a 17% reduction. These findings demonstrate the potential of vegetation, particularly at higher densities, to mitigate solitary wave energy and reduce run-up hazards. Furthermore, simulation results indicate that using vegetation as a retrofitting solution effectively mitigates overtopping rates, achieving a 37% reduction with minimal forest density (∅ = 0.023). These results underscore the effectiveness of nature-based interventions in enhancing coastal protection and resilience. • A WCSPH with porous model is developed to investigate wave attenuation by vegetation canopies. • The model integrates vegetation porosity, drag, and inertia forces into momentum equations. • Wave interactions with cylindrical and strip-type vegetation are implemented in WCSPH model. • Effects of mangrove density on solitary wave runup and energy dissipation is investigated. • Vegetation retrofitting on dykes reduce overtopping by 37% for minimum forest density. [ABSTRACT FROM AUTHOR]

Multi-component fluid mixing by buoyancy-driven circulation is a common engineering process. Buoyancy-driven flows have been studied extensively using mesh-based Eulerian methods, but challenges remain especially near the fluid component interface. Smoothed particle hydrodynamics (SPH) is a meshless Lagrangian method able to deal with large deformations and a changing interface between the fluid components. Herein, an SPH formulation is proposed by employing the Boussinesq approximation to model buoyancy-driven flows where the temperature evolves by a governing equation, as well as multiple components with variable viscosities. In addition, a new implementation of an adiabatic boundary condition in SPH is included by adapting the recently developed modified dynamic boundary condition. The SPH results are compared against reference solutions for 2-D and 3-D, single and multi-component cases such as a differentially heated cavity and a cylindrical tank. Agreement is found with reference solutions for differentially heated cavity cases, provided the ratio of smoothing length to particle size is sufficiently large. Furthermore, the combined volume fraction - finite time Lyapunov exponent mixing measure gives insight into the relative movement of components at both a local and global level. • New adiabatic SPH boundary condition simulates buoyancy-driven circulation. • New SPH formulation models multiple components with variable viscosities. • Validated against a range of 2-D & 3-D multi-component test cases. • Agreement is found with reference solutions for differentially-heated cavity cases. • New mixing measures quantify local composition and movement within mixture. [ABSTRACT FROM AUTHOR]

Depicting the co-occurrence of erosion and side slope failure during landslide dam breaches using numerical models remains a challenge. In this study, a 3D Smoothed Particle Hydrodynamics (SPH) framework is proposed by coupling the erosion and side slope failure processes. Erosion downcutting is depicted by calculating the washed-away materials due to shear forces exerted by overtopping flow, while side slope failure is simulated using the Drucker-Prager model. In the computation domain, the destabilized slope soil particles are identified, then set to deform like fluid, and subsequently mixed with the flow. The proposed model achieves a refined 3D simulation of breach channel morphology evolution. According to the driving factors, the breaching process can be divided into two stages: the erosion-dominated breach deepening stage, and the simultaneous deepening and widening stage driven by both erosion and side slope failure. Dam erodibility affects the rate of breaching, while soil cohesion influences the breach channel evolution. As soil erosion rate increases, peak discharge increases following a power function, while peak timing decreases according to a power function. As soil cohesion increases, side slope failure slows, resulting in steeper slopes and more pronounced "headcut" erosion, which shifts the slope failure mode from sliding to collapsing. [ABSTRACT FROM AUTHOR]

We present a poroelastic fluid–structure interaction δ -SPH model for simulating biofilm deformation and sloughing in microfluidic channels. Based on the mixture theory, this model accurately handles large deformations of solid structures and simultaneously simulates seepage flow within the porous biofilm and external flow. A key advantage of the model is its reliance on the solid phase material properties rather than the averaged properties of the biofilm, enabling the modeling of changes in porosity and biofilm material properties induced by loads. Model verification is achieved through two benchmark problems, followed by application to biofilm deformation and sloughing studies. The Young's modulus of biofilms is a key parameter of interest in many studies. Calibration of the biofilm's solid material elasticity modulus by using the presented model yields a value of 200 Pa, aligning with previous reports in literature. Additionally, the model is capable of simulating the sloughing process by evaluating local von Mises equivalent stress, reproducing different detachment patterns corresponding to various material strengths. This δ -SPH model offers an efficient numerical tool for biofilm analysis and is extendable to simulate other fluid–structure interaction problems involving porous media with large deformations, such as soil, debris flow, and biological tissues. [ABSTRACT FROM AUTHOR]

This study investigates the effects of drawdown flushing in hydraulic structures on sediment transport and morphological changes within and around reservoirs. Utilizing the Smoothed Particle Hydrodynamics (SPH) method, the research focuses on local erosion induced by drawdown flushing and examines the interaction between water and sediment. To validate sediment behavior, we analyzed a granular dam-break model using three rheological models: Herschel-Bulkley (H–B), Bingham, and μ(I). Two drawdown flushing scenarios are explored, considering mobile bed conditions at the reservoir's inlet and outlet. The study area is categorized into three zones: water, sediment, and the interface between water and sediment, with the μ(I) rheological model applied to the sediment portion. Within the interaction zone of sediment and water, the Shields parameter is defined based on Julien's relations to determine the yield stress of sediments. This value is then incorporated into the H–B model for sediment in this specific zone. Additionally, the drag force is introduced into the momentum equation within this zone. The study's findings are rigorously validated against existing numerical and experimental studies, affirming the credibility of the modeling approach. This research provides valuable insights into the complex dynamics of sediment transport during drawdown flushing in hydraulic structures. • Rheological models used to evaluate sediment behavior: Herschel-Bulkley (H-B), Bingham, and μ(I) models. • The study area in the drawdown flush is divided into three zones: water, sediment, and the water-sediment interface. • The μ(I) model is used in the sediment phase, and the H-B model is used at the water-sediment interface. • The study area is divided into segments, and backpressure is calculated in each segment for the sediment phase. • The Shields parameter, based on Julien's relations, and the drag force are applied at the water-sediment interface. [ABSTRACT FROM AUTHOR]

The objective of this research is to analyze vortex structures, lift, and drag coefficients, generated by a variety of obstacles in the context of a 2D laminar flow, comparing the results between the different cases. To that aim, numerical simulations using the Smoothed Particle Hydrodynamics (SPH) method have been carried out. The resulting data presented herein constitute a comprehensive study of the flow around obstacle problem in 2D using SPH. The influence of the geometry on vortex formation has been studied at the Reynolds number Re = 100. The results show a strong agreement with the values in the literature for cylinders and squares. This is a crucial stage for the validation of the methodology before expansion to various geometries, e.g. square-cylinder combinations, piggybacks, and horizontal spoiler configurations. Notably, this study introduces a novel horizontal spoiler configuration, as opposed to the conventional vertical orientation found in the literature. To the best of the authors' knowledge, this configuration is presented here for the first time. Among single shapes, the cylinder with a spoiler exhibits the highest value for the drag coefficient, being 34% greater when compared to the single cylinder configuration. In addition, regarding configurations with a pair of side-by-side obstacles, the results indicate a notable increase in the drag coefficient for the case of a larger cylinder coupled with a smaller cylinder at the smallest gap amongst the ones tested. Having a look at the lift coefficient, the results for the different shapes oscillate considerably compared to the case of a single cylinder used as a reference. The maximum increase is obtained for the cylinder with spoiler (122%) and the piggyback at the minimum distance tested (135%), suggesting that objects in close proximity (or joined together) highly influence lift inception. Conversely, the greatest reduction in lift oscillations is found for the both the piggyback (58%) and the cylinder with a square (52%) when the gap between the two objects increases. In terms of the Strouhal number, the highest value is observed for the case of a single cylinder. For the other shapes tested, the Strouhal number is reduced from 11% to 63%. Therefore, the study allows to analyze the influence of different shapes on lift and drag forces, vortex shedding frequencies, and the relation amongst them, helping to understanding interference effects and shape influence, thus offering relevant insights to various engineering applications. The SPH method is validated using two of the geometries considered. In addition, a verification analysis is carried out in the case of the single cylinder considering lift and drag coefficients as well as Strouhal number. These studies (validation and verification) constitute a comprehensive convergence analysis – customary in CFD applications – for the proposed numerical scheme, confirming the accuracy of the SPH results for this particular problem. The simulations were carried out using the AQUAgpuSPH software, developed at Universidad Politécnica de Madrid (UPM). • Vortex formation and forces from various obstacle shapes are studied with SPH. • Verification and validation studies are done for cylinder and square single shapes. • A novel spoiler with the highest drag coefficient among tested shapes is introduced. [ABSTRACT FROM AUTHOR]

This paper explores ship dynamics through numerical investigation using Smoothed Particle Hydrodynamics (SPH). To enhance the performance of SPH simulations, we implement the Dummy Particle Condition (DPC) floating-fluid interaction scheme in our numerical model, substituting the original Dynamic Boundary Condition (DBC). The accuracy of the updated model is validated by conducting a series of two-dimensional (2D) benchmark tests. Subsequently, based on both DBC and DPC, we simulate three-dimensional (3D) ship motion in a series of regular waves, including low and high waves, and compare the simulation results with model test data. It is demonstrated that, compared with the original DBC, the DPC floating-fluid interaction scheme effectively enhances SPH simulation performance in terms of ship dynamics for all wave conditions. Then, the correlation between simulation accuracy, wave height, and particle size in SPH is quantitatively discussed, and a clear relationship is observed for DPC results. • DPC is implemented in the SPH model to solve the unphysical gap problem caused by DBC. • The enhancements due to DPC is validated by the 2D benchmark tests. • 3D ship simulations show DPC better matches test data and is more robust. • Compared to low wave conditions, both DPC and DBC models perform better under high nonlinear wave conditions. • DPC shows a clear error relation to wave height/particle size ratio concerning ship dynamics. [ABSTRACT FROM AUTHOR]

Extraction of physical quantities such as flow depth and velocities, is one of the major purposes of geophysical flow numerical modeling and critical for estimating consequent impact forces and sediment entrainment. It is simple in nature for mesh-based models but presenting challenges in three-dimensional smoothed particle hydrodynamics (SPH) schemes. The difficulties lie in the substantial number of particles and their uneven spatial-temporal distribution, particularly over complex topography. Inspired by our previous surface cell (SC) -based approach, we propose a novel topography-based and vectorized algorithm that significantly enhances the ability to extract physical quantities over complex topography. In the proposed algorithm, geomorphologic characteristics are mathematically represented by topographical normal vectors. The correlations of physical quantities with distinct coordinate descriptions are established through the vectorization concept, ultimately leading to effective extraction of physical quantities in SPH form over complex topography. This algorithm provides an important tool to incorporate topography-linked physical models within discretized frameworks. To validate its effectiveness, we employed the algorithm to integrate the debris-flow entrainment law with our previous HBP-SPH model, utilizing the 2010 Yohutagawa debris-flow event in Japan as a case study. The results demonstrate a good agreement between the numerical simulation and on-site observation. Discussion regarding the applicability and limitation of the algorithm concludes the paper. • A novel topography-linked algorithm in 3D-SPH form is proposed to extract debris flow dynamics. • The PCA technique is used to represent complex bed surface by topographical normal vectors. • Vectorized operation is adopt to extract quantities in distinct coordinates, with CLL technique to organize data. • Two physic-based laws are integrated to simulate debris-flow entrainment over complex topography. • The 2010 Yohutagawa event is used to validate the effectiveness and applicability of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Water content is one important factor on which velocities, heights, and runout of debris flows and similar phenomena depend. To this purpose, we need two ingredients (i) a mathematical model describing the incorporation of water into the moving soil, which results in a change of water content, and (ii) a rheological model with properties depending on the water content. Modeling of such problems can be done either by using either a: (i) two phases approach, where velocities of solid and water may be different, using two sets of nodes, or (ii) two phases approach where velocities of both are assumed to be the same, using a single set of nodes. In both cases, the models have to implement a mechanism for the water inflow -or outflow-. We will modify both types of two phases models (one or two sets of nodes for solid and water) to include the change of water content due to water inflow. Implementation in the SPH requires extending the algorithm and updating the smoothing length because it is based on the mass of particles and their relative position. Updating the smoothing length when only changes mass is to be avoided. Regarding the rheological model, we will introduce a new model for frictional debris flows implementing a Voellmy coefficient which depends on water content. Alternatively, we will propose a more consistent model based on Bagnold's idea of introducing a 1D concentration parameter (λ). Finally, we will illustrate the proposed model capability with two examples, a dam break problem, and a real case in El Salvador where the water content played an important role in the propagation properties of a debris flow. [ABSTRACT FROM AUTHOR]

Recent refactoring of the GPUSPH codebase have uncovered some of the limitations of the official CUDA compiler (nvcc) offered by NVIDIA when dealing with some C++ constructs, which has shed some new light on the relative importance of the neighbors list construction and traversal in SPH codes, presenting new possibility of optimization with surprising performance gains. We present our solution for high-performance neighbors list construction and traversal, and show that a 4 × speedup can be achieved in industrial applications. • Neighbors list construction and traversal performance has a significant impact in SPH. • Using different compilers can help identify missed optimization opportunities. • Particle-centric may not be the most efficient parallelization for SPH on GPU. • Large single-GPU speed-ups can negatively affect multi-GPU scaling. [ABSTRACT FROM AUTHOR]

A large amount of wastewater from industrial and urban residents enters rivers and lakes through the sewage outlet, causing a deterioration of water quality near the sewage outlet. The smoothed particle hydrodynamics (SPH) formulation based on the open-source Fortran code SPHysics is extended to solve the advective diffusion for the evolution of the pollution distribution with the shallow water equation (SWE). Several numerical cases, such as the uniform flow and dam-break flows in one and two dimensions, are studied to verify the accuracy of the present SPH-SWE diffusion model. The results are in good agreement with the analytical solutions. The concentration of the negative value and oscillation could be avoided. It demonstrates that the current SPH-SWE diffusion model has good stability and reliability for solving the pollutant transport equation. The actual terrain case is also simulated to predict the concentration distribution of the river. The concentration is distributed in the center of the Nanmenxia River, where the flow velocity is relatively high. The simulation results are reasonable, implying that it has a high potential in predicting the diffusion process of pollutants in the actual terrain.

Particulate composites are one of the widely used materials in producing numerous state-of-the-art components in biomedical, automobile, aerospace including defence technology. Variety of modelling techniques have been adopted in the past to model mechanical behaviour of particulate composites. Due to their favourable properties, particle-based methods provide a convenient platform to model failure or fracture of these composites. Smooth particle hydrodynamics (SPH) is one of such methods which demonstrate excellent potential for modelling failure or fracture of particulate composites in a Lagrangian setting. One of the major challenges in using SPH method for modelling composite materials depends on accurate and efficient way to treat interface and boundary conditions. In this paper, a master-slave method based multi-freedom constraints is proposed to impose essential boundary conditions and interfacial displacement constraints in modelling mechanical behaviour of composite materials using SPH method. The proposed methodology enforces the above constraints more accurately and requires only smaller condition number for system stiffness matrix than the procedures based on typical penalty function approach. A minimum cut-off value-based error criteria is employed to improve the computational efficiency of the proposed methodology. In addition, the proposed method is further enhanced by adopting a modified numerical interpolation scheme along the boundary to increase the accuracy and computational efficiency. The numerical examples demonstrate that the proposed master-slave approach yields better accuracy in enforcing displacement constraints and requires approximately the same computational time as that of penalty method.

The planetary mechanism of shearer cutting department operates in harsh environment， suffers heavy impact load and complicated internal lubrication. In order to calculate the dynamic characteristics of planetary mechanism more accurately， a Smoothed Particle Hydrodynamics （SPH） method based on Abaqus is put forward. Taking MG400/951WD shearer as the engineering object， the three-dimensional assembly model of shearer is established by three-dimensional modeling software Pro/E， which is imported into Adams for multi-body dynamics simulation and output load file. The fluid-solid coupling model of planetary mechanism is established in Abaqus， and the dynamic analysis of non-linear gear meshing is carried out by using explicit dynamics solver， which verifies that the oil meshless feature has natural advantages over traditional dynamic analysis method and can be widely used in the dynamic study of key structural parts of industrial and mining equipment.

The accelerated global warming in recent years, and consequent melting of Arctic ice, has highlighted the significance of Arctic shipping lanes, resources, and military strategy. The presence of ice greatly affects the hydrodynamic behavior of objects entering water. This study investigates the ice model crevice effect on the vertical water-entry of a sphere through an experimental technique and smoothed particle hydrodynamic simulations. The results illustrate the cavity evolution process and determine the sphere's trajectory, effectively constructing the three-dimensional shape of the cavity under different values of the crevice spacing in the ice model. Furthermore, the air flow characteristics in the cavity are systematically explored. This study provides insights into the hydrodynamics and fluid–structure interactions involved in ice–water interfaces, with potential applications in fields including marine engineering and offshore structures. • An experimental platform simulating the water-entry of a sphere in an ice crevice environment was established. • The 3D shape evolution of the non-axisymmetric cavity was effectively reconstructed, and the flow characteristics were thoroughly examined. • The influence of crevice spacing on the characteristics of cavity evolution was summarized. [ABSTRACT FROM AUTHOR]

• CFD and SPH are rigorously tested and compared for complex single-phase and particle-liquid flows. • Laminar and turbulent flows, diverse rheologies and particle-liquid flow scenarios are studied. • CFD excels in accurately predicting all the various single-phase flows considered. • SPH captures well the fluid dynamics of laminar flows but shows limitations in the turbulent regime. • Coupling with DEM significantly improves both CFD and SPH for particle-laden flows. We investigate the effectiveness of two computational fluid dynamics (CFD) approaches: mesh-based CFD and meshfree particle-based smoothed particle hydrodynamics (SPH) for simulating pipe flows of varying complexity. The study covers laminar and turbulent flows, different fluid rheologies (Newtonian, power-law, Bingham plastic, Herschel-Bulkley), and different particle-laden scenarios, validated using experimental Lagrangian measurements obtained by positron emission particle tracking or available theoretical solutions, as appropriate. We assess these methods based on their ability to predict radial profiles of local phase velocity and concentration, as well as computational cost. In single-phase flows, CFD aligns well with experimental data and theoretical models. SPH exhibits boundary discrepancies due to no-slip condition approximations and limitations in turbulent flow simulation which need further development. Integrating the discrete element method (DEM) significantly enhances both techniques for particle-liquid flows. Mesh-based CFD is computationally efficient, while particle-based SPH can offer more insights into Lagrangian fluid dynamics. [ABSTRACT FROM AUTHOR]

In this work, the dynamics of a planing hull in regular head waves was investigated using the Smoothed Particle Hydrodynamics (SPH) meshfree method. The simulation of the interaction of such vessels with wave trains features several challenging characteristics, from the complex physical interaction, due to large dynamic responses, to the likewise heavy numerical workload. A novel numerical wave flume implemented within the SPH-based code DualSPHysics fulfills both demands, guaranteeing comparable accuracy with an established proprietary Computational Fluid Dynamics (CFD) solver without sharpening the computational load. The numerical wave flume uses ad hoc open-boundary conditions to reproduce the flow characteristics encountered by the hull during its motion, combining the current and waves while adjusting their properties with respect to the vessel’s experimental towing speed. It follows a relatively small three-dimensional domain, where the potentiality of the SPH method in modeling free-surface flows interacting with moving structures is unleashed. The results in different wave conditions show the feasibility of this novel approach, considering the overall good agreement with the experiments; hence, an interesting alternative procedure to simulate the seakeeping test in several marine conditions with bearable effort and satisfying accuracy is established.

Fissures and holes widely exist in rock mechanics engineering, and, at present, their failure mechanisms under complex compress and shear stress states have not been well recognized. In our work, a fracture mark, ξ, is introduced, and the kernel function of the smoothed-particle hydrodynamics (SPH) is then re-written, thus realizing the fracture modelling of the rock media. Then, the numerical models containing the fissures and holes are established, and their progressive failure processes under the compress and shear stress states are simulated, with the results showing that: (1) the improved SPH method can reflect the dynamic crack propagation processes of the rock masses, and the numerical results are in good agreement with the previous experimental results. Meanwhile, the improved SPH method can get rid of the traditional mesh re-division problems, which can be well-applied to rock failure modeling; (2) the hole shapes, fissure angles, fissure lengths, fissure numbers, and confining pressure all have great impacts on the final failure modes and peak strengths of the model; and (3) in practical engineering, the rock masses are in the 3D stress state, therefore, developing a high performance 3D SPH program and applying it to engineering in practice will be of great significance.

The explosive welding technology of titanium alloy Ti6Al4V/aluminum alloy 7075 is the most valuable research problem in the field of Ti/Al explosive welding. In this paper, the smooth particle hydrodynamics and molecular dynamics algorithms are used to conduct multi-scale numerical calculations on the explosive welding of Ti6Al4V and 7075. The interface morphology, interface atomic movement, lattice changes and crystal defects are comprehensively analyzed. With the calculation as a reference, the Ti6Al4V/7075 composite with a flat interface is prepared. The calculation results indicate that with the transformation of titanium aluminum crystal structure, a large number of various dislocations, mainly 1/6〈110〉dislocations, are generated on the titanium side; During explosive welding, uniform and stable element diffusion occurred. Element diffusion mainly occurred in the unloading stage when the pressure was 0. The melting zone and ablation zone were composed of TiAl and TiAl _3 , respectively; The fundamental reason for the combination of Ti6Al4V/7075 is the diffusion of elements and the solid-phase binding of atoms.

Affected by continuous heavy rainfall, a large number of landslide disasters occur every year in the Three Gorges Reservoir area, which causes serious property loss and casualties. In this study, we take a typical reservoir slope as an example. Firstly, the change of plastic zone of the slope under the action of continuous heavy rainfall before the failure is simulated based on the FEM method, considering the coupling of seepage field and stress field. Then, based on the smooth particle hydrodynamics method, HBP rheological model and Drucker–Prager yield criterion are used to simulate the dynamic catastrophic process of slope sliding after instability, and the time–space distribution of velocity field and accumulation form of the landslide are obtained based on the N-S equation. By analyzing the erosion behavior at the junction of various materials on the slope, the dynamic mechanism of the slope instability and slippage is revealed. [ABSTRACT FROM AUTHOR]

The traditional wave motion characteristic experiment has some problems, such as the loose connection between theory and experimental teaching, limitations of the experiment due to its site and time, and poor sense of participation and interaction. Focusing on the above problems, a virtual simulation experiment system for wave motion characteristics is designed and developed. The system uses virtual reality technology, cloud platform technology, and wave simulation technology. Taking the real laboratory as the prototype, the scene structure, instrument function, and water movement are simulated with high precision. The multimode fusion teaching method has expanded the experimental content, enriched the micro‐observation function and data collection categories, enhanced the interaction of the experimental process, and created a high‐quality immersive online teaching experience for the students. Since its inception, the experiment system has served six cycles of instruction and obtained good feedback from the teachers and students. During the period of the pandemic, it provides great support to experimental teaching and serves as a good supplement to the existing teaching system. Adhering to the "student‐centered" teaching principle, the teaching team will improve the experimental system constantly, cultivate the students' independent thinking and innovation abilities, help the students with their own personalized development, and contribute to the training of excellent engineers. [ABSTRACT FROM AUTHOR]

For some categories of aircraft, such as helicopters and tiltrotors, fuel storage systems must satisfy challenging crash resistance requirements in order to reduce or eliminate the possibility of fuel fires and thus increase the chances of passenger survival. Therefore, for such applications, fuel tanks with high flexibility (bladder) are increasingly used, which are able to withstand catastrophic events and avoid fuel leakages. The verification of these capabilities must be demonstrated by means of experimental tests, such as the cube drop test (MIL-DTL-27422). In order to reduce development costs, it is necessary to execute experimental tests with a high confidence of success, and, therefore, it is essential to have reliable and robust numerical analysis methodologies. The present work aims to provide a comparison between two explicit FE codes (i.e., Abaqus and Ls-Dyna), which are the most frequently used for such applications according to experimental data in the literature. Both codes offer different material models suitable for simulating the tank structure, and therefore, the most suitable one must be selected by means of a specific trade-off and calibration activity. Both are able to accurately simulate the complex fluid–structure interaction thanks to the use of the SPH approach, even if the resulting sloshing capabilities are quite different from each other. Additionally, the evolution of the tank's deformed shape highlights some differences, and, in particular, Abaqus seems to return a more natural and less artificial behavior. For both codes, the error in terms of maximum impact force is less than 5%, but, even in this case, Abaqus is able to return slightly more accurate results. [ABSTRACT FROM AUTHOR]

Rapid flow-like landslides, particularly debris flows and debris avalanches, cause significant economic damage and many victims worldwide every year. They are usually extremely fast with the capability of travelling long distances in short times, sweeping away everything in their path. The principal objective of this paper is to test the ability of the 'GeoFlow-SPH' two-phase model developed by the authors, to reproduce the complex behaviour of natural debris avalanches where pore-water pressure evolution plays a key role. To reach this goal, the model is applied to reproduce the complex dynamic behaviour observed in Johnsons Landing debris avalanche including the observed bifurcation caused by the flowing out of part of the moving mass from the mid-channel. Initial thickness deposit trim-line, distribution of deposit volume, and the average velocities were provided for this real case, making it an appropriate case to validate the developed model. The paper also contributes to evaluate the SPH-FD model's potentialities to simulate the structural countermeasure, like bottom drainage screens, used to reduce the impact of debris flows. The analysis of the results shows the adequacy of the proposed model to solve this complicated geophysical problem. [ABSTRACT FROM AUTHOR]

In the present study, a Smoothed Particle Hydrodynamic (SPH) method has been developed and used to model the penetration of a rigid body to the soil under a certain force. The soil is considered as a non-Newtonian fluid with a free surface condition. Although the SPH method involves some complexity, it is generally a simple and suitable method for modelling the contact of the rigid body to the soil; the free surface and the movement of the body can easily be implemented by the SPH method. By developing this method, the interaction of soil particles with a rigid body is investigated. The model considered for the soil is Bingham's model. In this study, the method is developed and validated with the previously available data and then used to model the problem of the rigid body contacting with soil. The purpose of this paper is to develop the SPH method in soil modelling and investigation of the amount of rigid body penetration in the soil. So, the penetration depth of the circular cylinder and rhombic cylinder as the rigid bodies in the collision to the soil are investigated and compared. [ABSTRACT FROM AUTHOR]

Debris flow is an important natural hazard in mountain zone because it can threaten human lives with very little warning. Since laboratory experiments on debris flows at real scale are difficult to perform, numerical simulations are important in evaluating the impact of such flows. Among several candidate models, the smoothed particle hydrodynamics (SPH) is a particular attractive numerical method for this purpose. SPH is a particle-based numerical hydrodynamic method originally developed in the astrophysical field before extension to elastic bodies. Several works have already tested the applicability of SPH to debris flow, despite there are only few detailed validations. In this report, thus, we aimed to check the applicability of SPH to debris flows. Since the accurate treatment of the elastic bodies tends to be computationally expensive, we have developed a massively parallel SPH code. A comparison between laboratory experiments and numerical simulations using SPH showed qualitatively similar features, though there are differences in quantitive comparisons. [ABSTRACT FROM AUTHOR]

Bird strikes are one of the most dangerous incidents occurring to aircraft engines and can inflict heavy casualties and economic losses. In this study, a smoothed particle hydrodynamics (SPH) mallard bird model has been used to simulate bird impact to rotary aero-engine fan blades. The simulations were performed using the finite element method (FEM) by means of LS-DYNA. The reliability of the material model and numerical method was verified by comparing the numerical results with Wilbeck's experimental results. The effects of impact and bearing parameters, including bird impact location, bird impact orientation, initial bird velocity, fan rotational speed, stiffness of the bearing, and the damping of the bearing on the bird impact to aero-engine fan blade are studied and discussed. The results show that both the impact location and bird orientation have significant effects on the bird strike results. Bird impact to blade roots is the most dangerous scenario causing the impact force to reach 390 kN. The most dangerous orientation is the case where the bird's head is tilted 45° horizontally, which leads to huge fan kinetic energy loss as high as 64.73 kJ. The bird's initial velocity affects blade deformations. The von Mises stress during the bird strike process can reach 1238 MPa for an initial bird velocity of 225 m/s. The fan's rotational speed and the bearing stiffness affect the rotor stability significantly. The value of bearing damping has little effect on the bird strike process. This paper presents a procedure for evaluating the strength of fan blades against bird strike in the design stage. [ABSTRACT FROM AUTHOR]

Flexible membranes are light structures anchored to the ground that protect infrastructures or dwellings from rock or soil sliding. One alternative to design these structures is by using numerical simulations. However, very few models were found until date and most of them are in 2D and do not include all their components. This paper presents the development of a numerical model combining Finite Element Modelling (FEM) with Smooth Particle Hydrodynamics (SPH) formulation. Both cylindrical and spherical failure of the slope were simulated. One reference geometry of the slope was designed and a total of 21 slip circles were calculated considering different soil parameters, phreatic level position and drainage solutions. Four case studies were extracted from these scenarios and simulated using different dimensions of the components of the system. As a validation model, an experimental test that imitates the soil detachment and its retention by the steel membrane was successfully reproduced.

A numerical investigation is conducted on a rotating engine blade subjected to a bird strike impact. The bird strike is numerically modelled as a cylindrical gelatine with hemispherical ends to simulate impact on a rotating engine blade. Numerical modelling of a rotating engine blade has shown that bird strikes can severely damage an engine blade, especially as the engine blade rotates, as the rotation causes initial stresses on the root of the engine blade. This paper presents a numerical modelling of the engine blades subjected to bird strike with porosity implemented on the engine blades to investigate further damage assessment due to this porosity effect. As porosity influences the decibel levels on a propeller blade or engine blade, the damage due to bird strikes can investigate the compromise this effect has on the structural integrity of the engine blades. This paper utilizes a bird strike simulation through an LS-Dyna Pre-post software. The numerical constitutive relations are keyed into the keyword manager where the bird’s SPH density, a 10 ms simulation time, and bird velocity of 100 m/s are all set. The blade rotates counter-clockwise at 200 rad/s with a tetrahedron mesh. The porous regions or voids along the blade are featured as 5 mm diameter voids, each spaced 5 mm apart. The bird is modelled as an Elastic-Plastic-Hydrodynamic material model to analyze the bird’s fluid behavior through a polynomial equation of state. To simulate the fluid structure interaction, the blade is modelled with Johnson-Cook Material model parameters of aluminium where the damage of the impact can be observed. The observations presented are compared to previous study of a bird strike impact on non-porous engine blades. ABSTRAK: Penyelidikan berangka telah dijalankan ke atas bilah enjin berputar tertakluk kepada impak pelanggaran burung. Pelanggaran burung tersebut telah dimodelkan secara berangka sebagai silinder gelatin dengan hujungnya berbentuk hemisfera demi mensimulasikan impaknya ke atas bilah enjin yang berputar. Pemodelan berangka bilah-bilah enjin yang berputar tersebut menunjukkan bahawa pelanggaran burung mampu menyebabkan kerosakan teruk terhadap bilah enjin terutamanya apabila bilah enjin sedang berputar oleh sebab putaran menghasilkan tekanan asal di pangkal bilah enjin. Kajian ini mengetengahkan pemodelan berangka ke atas bilah-bilah enjin tertakluk kepada pelanggaran burung terhadap bilah-bilah enjin yg mempunyai keliangan demi menyelidik dan menilai kerosakan kesan daripada keliangan tersebut. Keliangan juga mempengaruhi tahap-tahap desibel ke atas bilah kipas ataupun bilah enjin, kerosakan hasil serangan burung boleh menterjemah tahap ketahanan struktur integriti bagi bilah-bilah enjin tersebut. Penyelidikan ini mengguna pakai perisian “LS-Dyna Pre-post” untuk simulasi pelanggaran burung. Hubungan konstitutif berangka telah dimasukkan sebagai kata kunci di mana ketumpatan SPH burung, masa simulasi 10ms, dan halaju burung ditetapkan kepada 100 m/s. Bilah tersebut berputar pada 200 rad/s arah lawan jam dengan jejaring tetrahedron. Kawasan berliang atau kosong di sepanjang bilah ditetapkan diameternya kepada 5 mm, dan dijarakkan 5 mm di antara satu sama lain. Burung pula dimodelkan sebagai material “Elastic-Plastic-Hydrodynamic” untuk mengkaji sifat bendalir burung melalui persamaan polinomial. Demi mensimulasi interaksi struktur bendalir, bilah tersebut dimodelkan sebagai parameter aluminium material “Johnson Cook” di mana kerosakan daripada impak tersebut dapat diteliti. Penelitian-penelitian tersebut dibandingkan dengan kajian terdahulu ke atas serangan burung terhadap bilah-bilah enjin tidak berliang.

Lahars are rapid flows composed of water and volcaniclastic sediments, which have the potential to impact residential buildings and critical infrastructure as well as to disrupt critical services, especially in the absence of hazard-based land-use planning. Their destructive power is mostly associated with their velocity (related to internal flow properties and topographic interactions) and to their ability to bury buildings and structures (due to deposit thickness). The distance reached by lahars depends on their volume, on sediments/water ratio, as well as on the geometrical properties of the topography where they propagate. Here we present the assessment of risk associated with lahar using Vulcano island (Italy) as a case study. First, we estimated an initial lahar source volume considering the remobilisation by intense rain events of the tephra fallout on the slopes of the La Fossa cone (the active system on the island), where the tephra fallout is associated with the most likely scenario (e.g. long-lasting Vulcanian cycle). Second, we modelled and identified the potential syn-eruptive lahar impact areas on the northern sector of Vulcano, where residential and touristic facilities are located. We tested a range of parameters (e.g., entrainment capability, consolidation of tephra fallout deposit, friction angle) that can influence lahar propagation output both in terms of intensity of the event and extent of the inundation area. Finally, exposure and vulnerability surveys were carried out in order to compile exposure and risk maps for lahar-flow front velocity (semi-quantitative indicator-based risk assessment) and final lahar-deposit thickness (qualitative exposure-based risk assessment). Main outcomes show that the syn-eruptive lahar scenario with medium entrainment capability produces the highest impact associated with building burial by the final lahar deposit. Nonetheless, the syn-eruptive lahar scenario with low entrainment capacity is associated with higher runout and results in the highest impact associated with lahar-flow velocities. Based on our simulations, two critical infrastructures (telecommunication and power plant), as well as the main road crossing the island are exposed to potential lahar impacts (either due to lahar-flow velocity or lahar-deposit thickness or both). These results show that a risk-based spatial planning of the island could represent a valuable strategy to reduce the volcanic risk in the long term. [ABSTRACT FROM AUTHOR]

Oscillating wave surge converter (OWSC) is widely utilized to exploit energy from waves. Due to the wake effects, the layout of OWSCs will significantly affect the energy output of an OWSC farm. However, up to now the layout of OWSC farm was only determined empirically, and there was no quantitative layout optimization method for OWSC farm. The quantitative layout optimization needs analytical wake model for OWSC to conduct fast optimization iterations. However, there was still no analytical wake model for OWSC. Therefore, in this study, we proposed an analytical wake model regarding regular waves, based on which a quantitative method for optimizing the layout of OWSC farm was also proposed. It was found that the total energy outputs of the optimized layouts using the proposed method are significantly larger than those of the empirical ones, and increasing the spacing between the OWSCs in the bi-direction of wave propagation can greatly increase the total energy output. The proposed OWSC analytical wake model can predict the wave height changes with an accuracy of 94.73%. Innovatively, GPU-acceleration technology was utilized, and the GPU-based codes can run at least 1479 times faster than the CPU-based ones. Those implemented codes are opened for other researchers. • A novel analytical wake model is proposed to predict wave height changes in OWSC wakes. • An array optimization method is proposed for OWSCs to maximize their energy outputs quantitatively. • Staggered layouts of the OWSCs are recommended. • Increasing spacing between the OWSCs in the bi-direction of wave propagation can greatly increase total energy output. • GPU-based codes can run at least 1479 times faster than the CPU-based ones and are opened. [ABSTRACT FROM AUTHOR]

The turbulent plunging jet of a nearly incompressible fluid into a stagnant fluid is of great importance in many practical applications, especially for the engineering of hydropower. As an example, the dynamic load exerted by the impact of turbulent high-velocity jets into a pool must be estimated to evaluate the potential destabilization of a rock bed or dam's structure. Modelling plunging jets in the laboratory presents a challenge due to the complex two-phase environment, which requires models to be built at near-prototype scales. This paper deals with the application of a three-dimensional weakly compressible smoothed particle hydrodynamics (SPH) model to study a circular jet impinging into a water flat pool, at a near-prototype scale. To identify the level of reliability of the computed parameters, validation of the pool bottom pressures is carried out by comparison with existing experimental data. The self-similarity of the jet's centreline velocity is correctly reproduced and the computed maximum dynamic pressures near the stagnation point are reasonably accurate. The differences observed are mainly attributed to the non-consideration of the air phase. [ABSTRACT FROM AUTHOR]

Smoothed Particle Hydrodynamics (SPH) is fast emerging as a practically useful computational simulation tool for a wide variety of engineering problems. SPH is also gaining popularity as the back bone for fast and realistic animations in graphics and video games. The Lagrangian and mesh-free nature of the method facilitates fast and accurate simulation of material deformation, interface capture, etc. Typically, particle-based methods would necessitate particle search and locate algorithms to be implemented efficiently, as continuous creation of neighbor particle lists is a computationally expensive step. Hence, it is advantageous to implement SPH, on modern multi-core platforms with the help of High-Performance Computing (HPC) tools. In this work, the computational performance of an SPH algorithm is assessed on multi-core Central Processing Unit (CPU) as well as massively parallel General Purpose Graphical Processing Units (GP-GPU). Parallelizing SPH faces several challenges such as, scalability of the neighbor search process, force calculations, minimizing thread divergence, achieving coalesced memory access patterns, balancing workload, ensuring optimum use of computational resources, etc. While addressing some of these challenges, detailed analysis of performance metrics such as speedup, global load efficiency, global store efficiency, warp execution efficiency, occupancy, etc. is evaluated. The OpenMP and Compute Unified Device Architecture (C U D A) parallel programming models have been used for parallel computing on Intel Xeon (R) E5- 2 6 3 0 multi-core CPU and NVIDIA Quadro M 4 0 0 0 and NVIDIA Tesla p 1 0 0 massively parallel GPU architectures. Standard benchmark problems from the Computational Fluid Dynamics (CFD) literature are chosen for the validation. The key concern of how to identify a suitable architecture for mesh-less methods which essentially require heavy workload of neighbor search and evaluation of local force fields from neighbor interactions is addressed. [ABSTRACT FROM AUTHOR]

Many problems in geotechnical engineering involve large movements or rotations, examples include natural processes such as landslides, and man-made processes such as earthmoving and pile penetration. While the use of numerical modelling, primarily the finite element method (FEM), is now routine in geotechnical design and analysis, the limitations of conventional FEMs soon become apparent when attempting to model large deformation problems. For this reason, the search for alternatives remains a key goal of many geotechnical researchers, both to find accurate methods but also to develop efficient ones. In this review paper, prompted by Technical Committee 103 of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE), we survey the current state-of-the-art in numerical modelling techniques aimed at large deformation problems in geotechnics. The review covers continuum and discontinuum methods and provides a clear picture of what is and is not currently possible, which will be of use to both practitioners seeking suitable methods and researchers developing existing or new methods. [ABSTRACT FROM AUTHOR]

Dynamic boundary condition (DBC) has been widely used in SPH method. However, in certain situations, it was found that a few fluid particles could break through the boundary or were not reflected specularly. Of course, these phenomena are unphysical. To improve the performance of DBC, an improved dynamic boundary condition (IDBC) was presented in this paper. To prevent fluid particles from breaking through the boundary, the repulsive force of boundary particles was enhanced by expanding the equation of state into a higher order. To deal with the asymmetry of DBC, a rectangular support domain attached to boundary particles and a corresponding correction factor are proposed. The results of three test cases showed that the performance of IDBC was satisfied. [ABSTRACT FROM AUTHOR]