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As a popular meshfree particle method, the smoothed particle hydrodynamics (SPH) has suffered from not being able to directly implement the solid boundary conditions. This influences the SPH approximation accuracy and hinders its further development and application to engineering and scientific problems. In this paper, a coupled dynamic solid boundary treatment (SBT) algorithm has been proposed, after investigating the features of existing SPH SBT algorithms. The novelty of the coupled dynamic SBT algorithm includes a new repulsive force between approaching fluid and solid particles, and a new numerical approximation scheme for estimating field functions of virtual solid particles. The new SBT algorithm has been examined with three numerical examples including a typical dam-break flow, a dam-break flow with a sharp-edged obstacle, and a water entry problem. It is demonstrated that SPH with this coupled dynamic boundary algorithm can lead to accurate results with smooth pressure field, and that the new SBT algorithm is also suitable for complex and even moving solid boundaries.smoothed particle hydrodynamics (SPH), particle method, solid boundary treatment (SBT), coupled dynamic SBT Citation:

SUMMARYThis paper presents a computational model for free surface flows interacting with moving rigid bodies. The model is based on the SPH method, which is a popular meshfree, Lagrangian particle method and can naturally treat large flow deformation and moving features without any interface/surface capture or tracking algorithm. Fluid particles are used to model the free surface flows which are governed by Navier-Stokes equations, and solid particles are used to model the dynamic movement (translation and rotation) of moving rigid objects. The interaction of the neighboring fluid and solid particles renders the fluid-solid interaction and the non-slip solid boundary conditions. The SPH method is improved with corrections on the SPH kernel and kernel gradients, enhancement of solid boundary condition, and implementation of Reynoldsaveraged Navier-Stokes turbulence model. Three numerical examples including the water exit of a cylinder, the sinking of a submerged cylinder and the complicated motion of an elliptical cylinder near free surface are provided. The obtained numerical results show good agreement with results from other sources and clearly demonstrate the effectiveness of the presented meshfree particle model in modeling free surface flows with moving objects.

Violent free surface flows with strong fluid-solid interactions can produce a tremendous pressure load on structures, resulting in elastic and even plastic deformations. Modeling hydro-elastic problems with structure deformations and a free surface breakup is difficult by using routine numerical methods. This paper presents an improved Smoothed Particle Hydrodynamics (SPH) method for modeling hydro-elastic problems. The fluid particles are used to model the free surface flows governed by Navier-Stokes equations, and the solid particles are used to model the dynamic movement and deformation of the elastic solid objects. The improved SPH method employs a Kernel Gradient Correction (KGC) technique to improve the computational accuracy and a Fluid-Solid Interface Treatment (FSIT) algorithm with the interface fluid and solid particles being treated as the virtual particles against their counterparts and a soft repulsive force to prevent the penetration and a corrective density approximation scheme to remove the numerical oscillations. Three typical numerical examples are simulated, including a head-on collision of two rubber rings, the dam break with an elastic gate and the water impact onto a forefront elastic plate. The obtained SPH results agree well with experimental observations and numerical results from other sources.

Purpose -The purpose of this paper is to investigate different baffles on mitigating liquid sloshing in a rectangular tank due to a horizontal excitation and to find out the optimal selection of sloshing mitigation for practical applications. Design/methodology/approach -The numerical study is conducted by using a proven improved smoothed particle hydrodynamics (SPH), which is convenient in tracking free surfaces and capable of obtaining smooth and correct pressure field. Findings -Liquid sloshing effects in a rectangular tank with vertical middle baffles, horizontal baffles, T-shape baffles and porous baffles are investigated together with those without any baffles. It is found that the existence of baffles can mitigate sloshing effects and the mitigation performance depends on the shape, structure and location of the baffles. Considering the balance of sloshing mitigation performance and the complexity in structure and design, the I shaped and T shaped baffles can be good choices to mitigate sloshing effects. Practical implications -The presented methodology and findings can be helpful in practical engineering applications, especially in ocean engineering and problems with large sloshing effects. Originality/value -The SPH method is a meshfree, Lagrangian particle method, and therefore it is an attractive approach for modeling liquid sloshing with material interfaces, free surfaces and moving boundaries. In most previous literature, only simple baffles are investigated. In this paper, more complicated baffles are investigated, which can be helpful in practical applications and engineering designs.

Water entry problems are very common in engineering and sciences. When objects move with relatively high speed, bubble cavities will be generated, and the behavior of moving objects will also be affected conversely. In this paper, the water entry problems are studied using smoothed particle hydrodynamics (SPH) method, which has special advantages in modeling free surfaces, moving interfaces. First, an improved fluid–solid interface treatment algorithm is presented, whose effectiveness is validated by a water entry of a buoyant cylinder. Then the water entry with different velocities and directions are researched. It is found that the velocities and angles of the moving objects will affect the movement of the object greatly, and the SPH model can give optimal predication of these corresponding conditions.

This paper presents an implementation of an improved smoothed particle hydrodynamics (SPH) method for simulating violent water impinging jet flow problems. The presented SPH method involves three major modifications on the traditional SPH method, (1) The kernel gradient correction (KGC) and density correction are used to improve the computational accuracy and obtain smoothed pressure field, (2) a coupled dynamic solid boundary treatment (SBT) is used to remove the numerical oscillation near the solid boundary and ensure no penetration condition, (3) a free surface condition, which is obtained from the summation of kernel function and volume, is used to describe the water jet accurately. Different cases about violent impinging jet flows are simulated. The influences of impact velocity and angles are investigated. It is demonstrated that the presented SPH method has very good performance with accurate impinging jet patterns and pressure field distribution. It is also found that the pressure time histories of observation points are greatly influenced by the rarefaction wave from surrounding air. Closer distance from free surface can lead to quicker decay of the pressure time history.

In this paper, a general three-dimensional finite element model composed of eight-node three-dimension cohesive elements and eight-node solid elements with reduced integration for low-velocity impact analysis of composite materials is established. Firstly, the continuum damage mechanics is applied to simulate the initiation and evolution of the intra-laminar damage. Based on cohesive zone model, the cohesive elements are inserted between layers to predict the inter-laminar damage. Three failure criteria, including 2D Hashin, 3D Hashin and Chang-Chang criteria, are coded in VUMAT and are implemented in ABAQUS/Explicit. The numerical results of energy time curves, force time curves, force displacement curves and damage distribution under three impact energies (7.35 J, 11.03 J and 14.7 J) are in good agreement with previously published data in literature, which indicates that the finite element model is suitable for studying the mechanical response and damage distribution of composites laminates subjected to low-velocity impact. Moreover, the influence of stacking sequence and friction coefficient on mechanical response and damage distribution is analyzed. It is concluded that the composite laminate with a stacking sequence of [45°/0°/−45°/90°]S can reduce the area of damage region compared to [0°/90°]2S because the ±45° layer can improve the shear resistance of composite laminate. Also, the computation accuracy will be the best when the friction coefficient is adopted between 0.5 and 0.7.