An improved Riemann SPH-Hamiltonian SPH coupled solver for hydroelastic fluid-structure interactions

The stress intensity factors or strain energy release rate are typically used to characterise the stress field in the vicinity of a crack in fracture mechanics. One way to obtain the strain energy release rate in elastic–plastic fracture mechanics is from the stress and deformation field around the crack tip through the calculation of the J integral. The J-integral is contour independent, although the contour must start and end from a traction-free surface, such as the crack surface. Using Green’s theorem, the J-integral can be formulated as a surface or area integral, which makes it convenient for implementation in finite element method (FEM). More importantly, the J-integral calculation is insensitive to uncertainty of the exact crack tip location, can be applied for linear elastic analysis with small scale yielding and in an improved formulation for elastic plastic fracture. In short, the J-integral is an indispensable tool in the study of fracture mechanics. Despite the J-integral being widely used in FEM, including availability in most commercial FEM codes, there is currently no algorithm to calculate the J-integral in the Smoothed Particle Hydrodynamics (SPH) method. This is somewhat surprising since the SPH method, due to its meshless nature, has inherent advantages in dealing with cracks compared to mesh based methods such as FEM. In this paper we will therefore address this deficiency and develop an algorithm for calculation of the J integral in the SPH method. The implementation of his new alghorithm is based on a new definition of the weighting function q 1 , as appropriately normalised kernel function, which inherently satisfies all the specific requirements on q 1 : The function is sufficiently smooth in the J-integral area, it is equal to unit inside contour path of the integral and zero outside of the path. A further element of novelty is that in the current implementation, the gradient of this function is evaluated analytically rather than through a numerical approximation. The verification and validation of developed algorithm is based on simulation of the standard single edge notch tension test (SENT) under the plain strain conditions. The SPH results are compared to the FEM results for stress and displacement fields in the vicinity of the crack tip, as well as the J integral solutions. The SPH results demonstrated convergence and were within 2% of the converged FEM solutions. The validation also allows for the definition of simple guidelines for the definition of the J-integral area to achieve accurate results. The implementation is currently developed for linear elastic fracture mechanics applications, but its generalisation and application to elastic plastic fracture mechanics, including the combination with elastic plastic constitutive models is straightforward. • New algorithm to calculate J-Integral developed in Smoothed Particle Hydrodynamics (SPH). • New approach for calculating gradient of J-Integral weighting function q 1 analytically. • Confirmed accuracy of J-integral results from SPH compared to FEM results.

This paper presents some of our results in using of the Smoothed Particles Hydrodynamics (SPH) method for the numerical modelling of the detonation phenomena. The study of the detonation is very important for evaluation of different explosives and even for their design. The paper also presents, in a synthetically way, some fundamentals of the detonation. The numerical modelling of the detonation can be made by Finite Element Method (FEM), but using of the SPH method brings some important advantages because the large deformations, large distortions occur. If the FEM can be used in Arbitrary Lagrangian-Eulerian (ALE) formulation, the SPH method can easily works and next to it, some specific parameters (density variation, specific energy etc.) can be obtained and analyzed by post-processing. The numerical results (by FEM and by SPH method) are compared with theoretical results. The numerical study allowed us to analyse the influence of some explosive characteristics and of the circumstances (non confined and confined explosive) upon detonation parameters.

In this paper, a new bird model which combined the visco-elastic material properties and Smooth Particle Hydrodynamics (SPH) method has been proposed to simulate the bird features in high-speed conditions. A rigid plate impact test was adopted to compare the reaction of SPH and Lagrangian bird model. Compared with the results of Lagrangian bird model, new SPH model was more in line with the experimental data, and has better computational efficiency. The SPH bird model was further used to bird impacting with the wing leading edge by using finite element program LS-DYNA. Two kinds of leading edge structural enhancement programs have been proposed and carried out simulation of bird impact. Basis of calculation, the design parameters of experimental structure was determined and was produced to wait for final testing.

This paper discusses alternative Lagrangian formulations for smooth particle hydrodynamics method. These Lagrangian formulations are here employed in solving large strain problems that involve elasto-plastic and hyperelastic materials. It has previously been shown in the literature that the Lagrangian formulation for continuum eliminates the problem of tension instability which is generally coupled with Eulerian continuum formulation of smooth particle hydrodynamics and other meshless methods. This paper presents the details of the methodologies used in formulating Lagrangian smooth particle hydrodynamics method and their characteristics.

Comparison of MPS and SPH methods for solving forced motion ship flooding problems

Numerical simulations of water wave dynamics based on SPH methods

Ultrasonic-assisted grinding, a promising processing technique for machining hard and brittle materials, is already quite extensively employed in manufacturing industries. However, the material removal mechanism in ultrasonic-assisted grinding is not yet fully understood, which hinders its further application. This study investigates the material removal process in ultrasonic-assisted scratching (UAS) of SiC ceramics using both simulation and experiment method, in order to detail the material removal mechanism in ultrasonic-assisted grinding. A conventional scratching (CS) test was also carried out, but without ultrasonic vibration for comparison. The simulated workpiece is modeled by smooth particle hydrodynamic (SPH) particles. Results show the following: (1) the SPH method is suitable to investigate the material removal mechanism during ultrasonic-assisted grinding of hard and brittle materials. (2) The profile of scratching trace in ultrasonic vibration (UV) is a sinusoidal path. UV vibrating in the direction vertical to the workpiece results in material removed in either a continuous or a discontinuous mode. UV vibrating in the direction parallel to the workpiece expands the cutting area. (3) The groove depth in UAS is much bigger than that in CS. (4) UV results in the impact of the abrasive grain on the workpiece, causing the deformation field to spread from the impact site and leading to deeper scratching depths and larger radial and lateral cracks.

Numerical wave flume with improved smoothed particle hydrodynamics

A smooth particle hydrodynamic (SPH) method combined with the Herschel–Bulkley-Papanastasiou (HBP) model is proposed to simulate 3D concrete printing (3DCP). HBP model can better resolve the divergence of equivalent viscosity coefficient under small deformation and extend the compatibility of simulation to dilatant and pseudoplastic fluids, so it possesses natural superiority in modelling the 3D printing of cement-based material with visco-plastic rheology behaviour. The HBP-based SPH method considers the influence of the printing parameters including nozzle characteristics and printing-to-extrusion velocity ratio on the cross-sectional geometry of the deposited filament, and its outcomes agree qualitatively well with the experiment results. Furthermore, by utilising process parameters furnished by simulation cases, it is possible to determine the critical conditions under which filaments printed by different nozzle shapes are vulnerable to tearing, and the corresponding critical intervals when tearing occurs are also defined. 3DPC experiments verify these findings and confirm that SPH simulation provides additional information on the geometric characteristics of single-layer structures, as well as physical quantities that cannot be straightforwardly measured.

We have developed a microscopic blood model, that can express the deformation of an erythrocyte in micro-circulation, based on the Smoothed Particle Hydrodynamics (SPH) method. In the method, plasma fluid is discretized by SPH particles and an erythrocyte is modeled by internal SPH particles wrapped in elastic membrane particles. For verifying the model, in two dimensions, we numerically analyzed a popular phenomenon of erythrocyte; the tank tread motion of an erythrocyte under a constant shear field. The numerical results agreed well with the experimental data and the tank tread motion of erythrocyte was well realized by the model. From these results, it is confirmed that our blood model based on the SPH method can well express microscopic and rheological properties of erythrocytes.

Application of the Lagrangian meshfree approach to modelling of batch crystallisation: Part I—Modelling of stirred tank hydrodynamics

The boundary layer between an accretion disk and the surface of a compact object is simulated using the Smoothed Particle Hydrodynamics (SPH) method. The equations include radiation, which is treated in the flux limited diffusion approximation. The integrated equations and some numerical simulations of the 31) motion of the gas are presented.

Many numerical methods have been proposed in the efforts to revel the failure mechanism of the brittle materials, such as rock and concrete, under various loading conditions. It is of continuous interests on properly modeling the heterogeneous microstructure and to account for its effects on the macroscopic material failure; and effectively tackling the initial and created discontinuities, such as fractures and fragmentations in the failure process. In this thesis, a numerical approach based on the mesh-free Smoothed Particle Hydrodynamics (SPH) method is developed that is able to simulate the dynamic failure of brittle materials by capturing the detailed occurring sequence of the microscopic cracks as well as the macro mechanical response. An elasto-plastic damage model based on the extension of the Unified Strength Theory is adopted in order to better reflect the strength behavior of the materials. To model the material heterogeneity, a statistical approach has been utilized. In addition, a polymineral model for the multi-phased materials has been incorporated to simulate heterogeneous materials with different compositions more appropritely. A series of numerical simulations in 2-D and 3-D on rock-like material failures are performed using the developed program. The influences of material heterogeneity as well as the strain rate on the material fracture process and its dynamic strength are investigated and compared with experimental results. Comparisons show that they agree well qualitatively. Particularly, the results reveal that the strain rate dependency of the dynamic tensile and compressive strength might be ascribed to the apparent confining pressure effects by the rapid loading. It shows that the developed program is very promising in conducting such kind of simulations and deserves further improvements for many other applications.

Flow physics and chine control of the water spray generated by an aircraft rigid tire rolling on contaminated runways

In this study, the fluid-structure interactive behavior by using the Westergaard approach and the Smoothed Particle Hydrodynamics (SPH) method of a 1000 m3 reinforced concrete (RC) elevated water tank under different seismic activities i.e., Kocaeli, Van, Kahramanmaraş and Kobe earthquakes was investigated. In the SPH method, the resulting hydrodynamic pressures were applied to the interior of the wall of the structure as an external force which is made as mass additions to the tank walls in Westergaard approach. With the help of software developed, the load carrying system of the elevated water tank was modeled using the MATLAB Partial Differential Equation Toolbox (PDE) software, based on the finite element method, and its verification was made by comparing with ANSYS software model. Dynamic condensation method was used to perform time history analyses for the cited earthquakes. The time-dependent solutions of partial differential equations are solved with the help of ODE45 functions based on Runge-Kutta method, by arranging the equation of motion in state-space format. The cited tank was analyzed linearly under different seismic activities for empty, half-filled (50%) and full-filled (100%) cases and the obtained results were compared with each other. It has been concluded that considering nonlinear behavior of the fluid during the earthquake with the SPH method provided consistency with the real behavior of RC elevated water tanks and gave more realistic results than the traditional Westergaard approach.