Particle Hydrodynamics Method Research Articles

Simulation Analysis of Concrete Pumping Based on Smooth Particle Hydrodynamics and Discrete Elements Method Coupling

With an increase of suction efficiency of fresh concrete pumping in confined spaces, the laminar flow state will be damaged by the return flow caused by distribution value direction changes and concrete gravity. This is a fact, but one which is rarely studied. In this work, the flow state, flow velocity, and suction efficiency of fresh concrete pumping are simulated using the coupled smooth particle hydrodynamics and Discrete Elements Method (SPH-DEM). The rheological parameters and Herschel-Bulkley-Papanastasiou (HBP) rheological model are adopted to simulate fresh concrete in the numerical simulation model. The study reveals that the error between the slump experimental result and that obtained by the HBP model is negligible. A model is therefore established for numerical simulations of the suction efficiency of fresh concrete pumping. An experimental concrete pumping platform is built, and the pressure and efficiency data during pumping are collected. A comparison of the numerical simulation with experimental results shows that the error is less than 10%.

An Experimental and Numerical Simulation Study of Single Particle Impact during Detonation Spraying

A comparison of the numerical simulation and an experimental study of the collision of the particles and the substrate during detonation spraying is presented. The spraying regimes were chosen to provide unmelted, partially melted, and completely molten particles. The numerical simulation was performed using the smoothed particle hydrodynamics (SPH) method with velocity and temperature settings as initial conditions. Good agreement was obtained between the simulation results and the experimental data, making the SPH simulation suitable for analysis of the deformation of particles and the substrate during detonation spraying. Information about the particle’s shape evolution during the collision is presented. An increase in temperature and plastic strain is analyzed at different points of the particle and substrate. Under certain spraying regimes, it is possible to melt a solid particle due to its high-strain-rate deformation, but no melting of the substrate was observed during the simulation.

Two-Phase Smoothed Particle Hydrodynamics Modelling of Hydrodynamic-Aerodynamic and Wave-Structure Interaction

A two-phase (air and water) smoothed particle hydrodynamics (SPH) method is employed to study the hydrodynamic-aerodynamic and wave interaction with fixed and floating structures in a wave basin. The method is first verified for a classical two-phase dam-breaking. A mirror-open boundary is implemented at the top and left sides of a two-phase wave basin with a piston to generate a second-order regular wave. It is observed that, compared to the single-phase simulation, the two-phase one obtains a smoother water surface and prevents the non-physical water splash when interacting with the sloped dissipative beach. This wave basin is also used to investigate wave-structure problems such as wave interaction with a rigid cantilever beam fixed to the basin bottom and downstream of the wave-maker mechanism and the dynamics of a single floating box and two floating boxes in the waves. A typical wave-structure interaction period is captured and described using pressure contours and velocity vectors at three selected instants for the wave-rigid cantilever beam case. With the increase of the structure’s height, the wave height after the structure decreases, but no evident variation is found when changing its thickness. Besides the hydrodynamics interaction, a periodical collision is observed between the two floating boxes on the wave surface.

Flocking Bird Strikes on Engine Fan Blades and Their Effect on Rotor System: A Numerical Simulation

Bird strikes are a common, serious, and devastating event in aviation accidents, and multi-bird strikes are also frequently reported. A numerical multi-bird-strike simulation was performed to investigate the effect of flocking birds striking on engine blades. The smooth particle hydrodynamics (SPH) method was adopted in the hemispherical-ended bird substitute model, and the finite element method (FEM) with EOS state equation was adopted for the fan model as well. Impact analyses have been presented using different flocking birds and impact location distributions. A “0-2-1” supported rotor system dynamic model was established to study the effect of the multi-bird-strike impact forces on the rotor system. The results show that bird-strike severity is related to the impact location distribution, with blade-root impacts being the most dangerous. The small flocking bird strikes had little effect on the fan compared to the cases of medium flocking birds and the large single bird. The dynamic response of the fan to the small flocking birds was the same as without a bird strike, while the other cases changed the motion period and excited the rotor first-order vibration.

ISPH Simulation of Solitary Waves Propagating Over a Bottom-Mounted Barrier With k–ε Turbulence Model

Solitary wave propagating over a bottom-mounted barrier is simulated using the Incompressible Smoothed Particle Hydrodynamics (ISPH) method in order to study the generation and transport of turbulence associated with flow separation around submerged structures. For an accurate capture of turbulence characteristics during the wave propagation, rather than employing the standard sub-particle scale (SPS) model, the k-ε turbulence model is coupled with the numerical scheme. The results of the numerical model are compared with experimental data, and good agreement is observed in terms of mean velocity, free surface elevation, vorticity fields and turbulent kinetic energy. The numerical model is then employed to investigate the effects of wave non-linearity and geometrical size of the submerged barrier on the flow separation; and calculate the reflection, dissipation and transmission coefficients to evaluate the importance of energy dissipation due to the generation of vortices. The results of this study show that the developed ISPH method with the k-ε turbulence closure model is capable of reproducing the velocity fields and the turbulence characteristics accurately, and thus can be used to perform predictions of comprehensive hydrodynamics of flow-structure interactions in the urban hydro-environment systems.

Extraction of New Applicable Dimensionless Relations in the Wedge Impact Problem Using WCSPH Method

Impact problem associated with water entry of a wedge has important applications in various aspects of naval architecture and ocean engineering. In the present study, the 2DOF (2 Degrees of Freedom) wedge impact problem into the water with various wedge deadrise angles and impact velocities is investigated using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method. Artificial viscosity and density correction are used to create stability and also to prevent the penetration of fluid particles into the solid boundary. Solving the impact problem is very time-consuming, therefore extracting new mathematical relations can be very useful to calculate some important and applicable parameters in a certain range of wedge angles and impact velocities. In the present research, some new dimensionless applicable relations using the Buckingham π theorem are extracted to investigate important parameters such as acceleration and slamming force in general cases of a wedge impact problem. Then, these mathematical relations are validated by the results obtained from the simulations.

Моделирование воздействия объекта малого космического мусора на защитный экран трансформируемой ловушки

The growth in the number of space debris, especially small-size debris undetectable by radars, urges the development of protective equipment for the crucial satellites and space station. Passive multilayer shields are the most effective means of protection. As the shields are big, it makes sense to make them out of flexible composite materials that allow them to be deployed in orbit. The article determines the loads acting on the composite load-bearing frame of the trap for small-size debris during impact. For a rational choice of the structural trap layout and optimization of its design parameters it is critical to know these loads. The hypervelocity impact of the projectile on the shield was modeled in the Altair Radioss software package using a combined model based on the Smoothed Particle Hydrodynamic (SPH) method and mesh finite elements. The simulation of the shield penetration at various locations was carried out. For each simulation case, a time history of the reaction force in the attachment point of the protective shield to the load-bearing frame was determined. It was shown that the maximum load of about 2000 N acts for around 6 milliseconds on the joint closest to the impact point for the debris projectile size of 10 mm and velocity of 2 km/s.

Utilizing Artificial Neural Network for Load Prediction Caused by Fluid Sloshing in Tanks

In this research, neural network models were used to predict the action of sloshing phenomena in a tank containing fluid under harmonic excitation. A new methodology is proposed in this analysis to test and simulate fluid sloshing behavior in the tank. The sloshing behavior was first modeled using the smooth particle hydrodynamics (SPH) method. The backpropagation of the error algorithm was then used to apply the two multilayer feed-forward neural networks and the recurrent neural network. The findings of the SPH process are employed in the training and testing of neural networks. Input neural network data include the tank position, velocity, and acceleration, neural output data, and fluid sloshing curve wave position. The findings of the neural networks were correlated with the experimental evidence provided in the literature. The findings revealed that neural networks can be used to predict fluid sloshing.

General isotropic micropolar fluid model in smoothed particle hydrodynamics.

The smoothed particle hydrodynamics (SPH) method is used in this paper to model micropolar fluids, with emphasis on their dissipation mechanisms. To this aim, a dissipation function is defined at the particle level which depends on the relative velocity between particles but also on an additional spin degree of freedom, which modifies such relative velocity as well as introduces spin-related intrinsic dissipation mechanisms, comparable to those related to the rate of deformation tensor in Newtonian fluids. This dissipation function is then incorporated within the Lagrangian formalism, leading to a set of SPH particle equations to describe the dynamics. A continuous integral SPH version of the scheme is obtained with a bottom-up derivation which guarantees the consistency of the SPH term. The model is then enriched with two additional terms based exclusively on the spin derivatives, which grant it the maximal generality as an isotropic model for micropolar fluids. Finally, numerical verification and validation tests are documented that show that SPH is capable of accurately modeling this type of dynamics.

Numerical Analysis of the Hydraulic Fracturing of Pressure Tunnel Lining Based on the 2P-IKSPH Method

In order to investigate the fracture mechanisms of the pressure tunnel lining under water-stress coupling, based on the traditional smoothed particle hydrodynamics (SPH) method, the solid-water particle interaction method, and the particle damage conversion algorithm are proposed to realize the hydraulic fracturing process, which is called the 2P-IKSPH method. The “particle domain searching method,” the “birth-and-death particle method,” and the “group discrimination searching method” have also been proposed to realize the simulations of complex processes of excavation, lining, and operation of the hydraulic tunnel. Taking the Guzeng hydraulic tunnel as an engineering example, the hydraulic fracturing of tunnel lining under different conditions is numerically simulated. Results show the following: (1) the 2P-IKSPH method can dynamically reflect the stress wave propagation processes of surrounding rock and the damage process of tunnel lining. (2) The lining damage mainly occurs on the vault and the arch foot. (3) The critical internal water pressure increases with the increase of the tunnel buried depth and the thickness of lining, but increases first and then decreases with the increase of the surrounding rock mass grade. The research results can provide some references for the optimization designs of tunnel lining and reinforcement of similar projects. Meanwhile, developing 3D parallelization program based on 2P-IKSPH will be the future research directions.

New Kernel Function for the Approximation of Third Order Derivatives

A new kernel function is developed to approximate the third order derivative by mean of the Smoothed Particle Hydrodynamics (SPH) method. It has the advantage to be efficiently used with gridded data and random distributions. Due to the discrepancy of the particles in the former distribution, we extended the use of the CSPM method for the approximation of third order derivatives. Our new kernel function provides three accurate numerical schemes, in conjunction with the trapezoidal rule, Simpson’s rule and the CSPM method respectively.

Failure Mechanism and Effect of Nozzle Parameters on Abrasive Water Jet Rock Breaking

Abrasive Water Jet (AWJ) technology has vast application prospects in the assisted drill-blasting of tunnel excavation, with the advantages of fast-breaking speed, low tool wear, less dust, and good mobility. Nevertheless, AWJ technology has some limitations and shortcomings, such as the small effective fracturing range and parameter mismatch, which influence the fracturing effect of AWJ. To solve the abovementioned issues, it is necessary to study the failure mechanism of rock impacted by AWJ and nozzle parameter effects on rock fragmentation. Based on the coupling algorithm of Smooth Particle Hydrodynamics and Finite Element Method (SPH-FEM), in this research, the numerical model of AWJ impacting rock was established, and the result was verified with Computed Tomography (CT) scanning after the AWJ impacting rock experiment and image processing technology. Through the analysis of the stress characteristics of typical particles in the rock model at different stages and positions, the formation and expansion mechanisms of the crater and the cracks were revealed. Additionally, in this research, the comprehensive damage factor of rock (X) representing the fragmentation degree was defined. By comparatively analyzing X-values with certain technical parameters of AWJ, the importance ranking of the nozzle parameters, the effect of each nozzle parameter on the rock fragmentation, and the optimal parameter combination were also investigated.

Enhancing the Iterative Smoothed Particle Hydrodynamics Method

Motivated by recent research on the iterative approach proposed for the smoothed particle hydrodynamics (ISPH) method, some ideas to improve the process are introduced. The standard procedure is enhanced iterating on the residuals preserving the matrix-free nature of the process. The method is appealing providing reasonable results with disordered data distribution too and no kernel variations are needed in the approximation. This work moves forward with a novel formulation requiring a lower number of iterations to reach a desired accuracy. The computational procedure is described and some results are introduced to appreciate the proposed formulation.

Studies of the Fragmentation of Spherical Aluminum Projectiles on a Heavy Mesh at Velocities of up to 7 km/s

The results of experimental studies and numerical simulation of the fragmentation of aluminum alloy projectiles on a tungsten mesh bumper at impact velocities of up to 7 km/s are presented. The projectiles are accelerated by a two-stage light-gas gun. X-ray photography is used to observe the state of a projectile before its impact on the mesh bumper and the process of its fragmentation. The parameters of the cloud of fragments of the projectile are recorded using a thick witness plate made of AMg6 alloy placed behind the mesh bumper. Numerical simulation is performed by the smoothed particle hydrodynamic (SPH) method. Specific features of the morphology of the cloud of fragments are pointed out, and the velocities of the fragments in different parts of the cloud, as well as the arising cumulative effect, are estimated. The experimental results are compared with the results of numerical simulation.

Lagrangian radial basis function‐based particle hydrodynamics method and its application for viscous flows

AbstractA Lagrangian radial basis function‐based particle hydrodynamics method (RBFPH) is proposed. In RBFPH method, the differential quadrature technique is combined with radial basis function (RBF) to obtain the meshless high‐dimensional derivative approximations for randomly distributed particles; a particular solution of RBF is chosen to ensure the positive definite of the interpolating matrix. Like the conventional RBF, RBFPH has the advantages of simple form, isotropy and high accuracy, and is suitable for numerical calculation. Moreover, all particles in RBFPH can move with the fluid, so RBFPH may conveniently compute complex flows with the moving boundary. A series of numerical examples are conducted to test the accuracy of RBFPH, and the results show the RBFPH has second‐order convergence, which shows its great advantage in terms of accuracy. The RBFPH is validated by its application to the simulations of Taylor–Green flow, lid driven shear cavity flows, stretching of a free‐surface circular fluid patch and flows around a cylinder. Excellent agreements with analytical solutions and reference results indicate that the proposed method has a promising application in simulating viscous flows with the moving boundary, large deformation, and free surface.

Kinematic and dynamic analysis of dam break flow impact on vertical walls using weakly compressible SPH

This article presents the kinematic and dynamic analysis of a dam break flow based on data obtained from numerical solutions by the smoothed particle hydrodynamics (SPH) method. The method and original algorithms necessary for correct pressure evaluation are thoroughly described. The pressure evaluation method consists of data reading using virtual sensors and filtration in the time domain using the weight function. A simple convergence study showing the independency of the evaluated parameters of spatial resolution is presented together with validation of the introduced methods and algorithms using a simple hydrostatic problem and experimental data available in the literature. We focus on two parameters that describe the problem: distance of the downstream vertical wall from the edge of the liquid column and the column’s height to width ratio. We found that the impact can be divided into three consecutive phases characterized by specific kinematic (flow patterns) and dynamic (exerted pressure and forces) behavior and different roles of the investigated parameters during these phases. During the early stages of an impact, the column’s distance from the vertical wall plays a major role. A dependency between the column distance and the force peak in this stage was identified in the form of a power function. In the second stage, when a rolling wave emerges, the vertical wall position influences the shape of the wave and the pressure distribution on the wall. The total force is greater in this phase for lower column height to width ratios due to the higher total momentum of the liquid. In the third stage, when the rolling wave impacts the liquid surface, the employed methodology with two-dimensional solution and free-surface approach seems to reach its limits of applicability. A more complex modelling would be necessary to capture this phase of the impact properly.

Simulation Study of Smoothed Particle Hydrodynamics (SPH) Method in Plasma Spheroidization of W-Ni-Fe Ternary Alloys

Simulation Study of Smoothed Particle Hydrodynamics (SPH) Method in Plasma Spheroidization of W-Ni-Fe Ternary Alloys

Numerical Simulation of Water Spray Generated by Aircraft Multi-Wheels

When the tire of aircraft landing gear passes through the contaminated runway, besides the side water spray, the water spray between the multi-wheels will collide and form the pattern similar to the tail of the rooster. This kind of water spray is called the cock tail flow. In this paper, numerical analysis is used to study the formation process of the cock tail flow caused by the main aircraft tires, and the water is simulated by smoothed particle hydrodynamics (SPH) method. According to the results of numerical simulation, the pattern and velocity distribution of cock tail flow are analyzed. The effects of water depth, tire spacing and tire speed on the pattern and velocity distribution of cock tail flow are obtained, and the formation mechanism of cock tail flow is revealed. It is preliminarily verified that numerical simulation using SPH method can analyze the specific problems of the tire including different configurations.

Numerical simulation of the joining interface of dissimilar metals in vaporizing foil actuator welding: Forming mechanism and factors

Abstract Predicting and controlling the joining interface are the main difficulties in impact welding dissimilar metal. In this study, the smoothed particle hydrodynamics (SPH) method was used to simulate the Cu/Ti wave interface forming process during high-rate impact welding. This process simulation was verified by vaporizing foil actuator welding experiments. The forming mechanism and factors influencing the characteristics of joining interface were simultaneously investigated. Results showed that, joining interface wave forming depended on the density ratio of the flyer sheet to the target sheet. Wave formation distance was mainly related to materials yield stress. The wavelength and amplitude of wavy characteristic increased with the impact angle and impact speed. Temperature distribution analyses proved that the average temperature of the vortex at the welding interface was higher than that in the other areas, indicating that the inter-metallic distribution was mainly in the vortex of the wave interface. Investigation of the moving trail of metal particles verified that the interaction of interface materials was caused by embedded deformation.

АНАЛИЗ СУЩЕСТВУЮЩИХ ЧИСЛЕННЫХ МЕТОДОВ МОДЕЛИРОВАНИЯ ВЗАИМОДЕЙСТВИЯ РАБОЧИХ ОРГАНОВ ЗЕМЛЕРОЙНЫХ И ПОЧВООБРАБАТЫВАЮЩИХ МАШИН С ПОЧВЕННЫМИ СРЕДАМИ

Carrying out theoretical studies of the working processes of various machines and units today has ample opportunities when using modern computer technologies. The use of programs greatly speeds up the study of complex systems under study. The use of simulation methods is advisable when the cost of carrying out real experimental research is high or, due to certain circumstances, making research on a real system impossible, and the calculation of the analytical model will allow many assumptions and approximations that will affect the entire system and change it. In the article, special attention is paid to the selection of the most suitable modeling method for studying the process, liquidation of a forest fire with a flow of soil, using serial software products. The analysis of existing numerical methods for modeling the interaction of working bodies of earth-moving and tillage machines with soil media is carried out. The studies performed by the discrete element method (DEM), the finite element method (FEM), the computational fluid dynamics (CFD) method, and the smooth particle hydrodynamics (SPH) method are analyzed. Conclusions are drawn on the prospects for the applicability of each of the methods for modeling the system of processes of processing and throwing soil.