Surface Tension Model Based on Implicit Incompressible Smoothed Particle Hydrodynamics for Fluid Simulation

In order to capture stable and realistic microscopic features of fluid surface, a surface tension and adhesion method based on implicit incompressible SPH （smoothed particle hydrodynamics） is presented in this paper. It gives a steady and fast tension model and can solve the problem of not considering adhesion. Molecular cohesion and surface minimization are considered for surface tension, and adhesion is added to show the microscopic characteristics of the surface. To simulate surface tension and adhesion stably and efficiently, the surface tension and adhesion model is integrated to an implicit incompressible SPH method. The experimental results show that the method can better simulate surface features in a variety of scenarios compared with previous methods and meanwhile ensure stability and efficiency.

Numerical modeling of sediment transport based on unsteady and steady flows by incompressible smoothed particle hydrodynamics method

The purpose of the present paper is to introduce a simple two-part multi-phase model for the sediment transport problems based on the incompressible smoothed particle hydrodynamics（ISPH） method. The proposed model simulates the movement of sediment particles in two parts. The sediment particles are classified into three categories, including the motionless particles, moving particles behave like a rigid body, and moving particles with a pseudo fluid behavior. The criterion for the classification of sediment particles is the Bingham rheological model. Verification of the present model is performed by simulation of the dam break waves on movable beds with different conditions and the bed scouring under steady flow condition. Comparison of the present model results, the experimental data and available numerical results show that it has good ability to simulate flow pattern and sediment transport.

Simulation of Wave Impact on a Horizontal Deck Based on SPH Method

A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely used in the free-surface hydrodynamic flows with good accuracy. The improvement includes the employment of a corrective function for enhancement of angular momentum conservation in a particle-based calculation and a new estimation method to predict the pressure on the horizontal deck. The simulation results show a good agreement with the experiment. The present numerical model can be used to study wave impact load on the horizontal deck.

Simulation of Wave Impact on Three-Dimensional Horizontal Plate Based on SPH Method

An improved three-dimensional incompressible smooth particle hydrodynamics(ISPH)model is developed to simulate the impact of regular wave on a horizontal plate.The improvement is the employment of a corrective function to enhance angular momentum conservation in a particle-based calculation.And a new estimation method is proposed to predict the pressure on the horizontal plate.Then,the model simulates the variation characteristics of impact pressures generated by regular wave slamming.The main features of velocity field and pressure field near the plate are presented.The present numerical model can be used to study wave impact load on the horizontal plate.

Incompressible SPH simulation of solitary wave propagation on permeable beaches

Wave propagation on uniformly sloped beaches is a canonical coastal engineering topic that has been studied extensively in the past few decades.However,most of these studies treat beaches as solid boundaries even though they are often made of porous materials,such as sediment and vegetation.Permeable beaches struck by tsunami-like waves have not been adequately investigated.It is expected that the degree of penneability plays a crucial role in mitigating the impact of the wave.This study examines solitary wave run-ups on sandy beaches using an incompressible smoothed particle hydrodynamics(ISPH)model.The permeability of the beach is considered to be directly related to the diameter of its constituent sand particles.To obtain a satisfactory pressure field,which cannot be achieved using the original ISPH algorithm,the source term of the pressure Poisson equation has been modified based on a higher-order source-term expression.Flows within the porous medium are computed in the same framework as those outside the porous medium.In the current model,no transition zone is needed at the boundary of the porous structure.The wave-attenuation effect of the porous medium is discussed,with a particular focus on the relationship between the mn-up height and grainsize.

Towards development of enhanced fully-Lagrangian mesh-free computational methods for fluid-structure interaction

Simulation of incompressible fluid flow-elastic structure interactions is targeted by using fully-Lagrangian mesh-free computational methods. A projection-based fluid model（moving particle semi-implicit（MPS）） is coupled with either a Newtonian or a Hamiltonian Lagrangian structure model（MPS or HMPS） in a mathematically-physically consistent manner. The fluid model is founded on the solution of Navier-Stokes and continuity equations. The structure models are configured either in the framework of Newtonian mechanics on the basis of conservation of linear and angular momenta, or Hamiltonian mechanics on the basis of variational principle for incompressible elastodynamics. A set of enhanced schemes are incorporated for projection-based fluid model（Enhanced MPS）, thus, the developed coupled solvers for fluid structure interaction（FSI） are referred to as Enhanced MPS-MPS and Enhanced MPS-HMPS. Besides, two smoothed particle hydrodynamics（SPH）-based FSI solvers, being developed by the authors, are considered and their potential applicability and comparable performance are briefly discussed in comparison with MPS-based FSI solvers. The SPH-based FSI solvers are established through coupling of projection-based incompressible SPH（ISPH） fluid model and SPH-based Newtonian/Hamiltonian structure models, leading to Enhanced ISPH-SPH and Enhanced ISPH-HSPH. A comparative study is carried out on the performances of the FSI solvers through a set of benchmark tests, including hydrostatic water column on an elastic plate,high speed impact of an elastic aluminum beam, hydroelastic slamming of a marine panel and dam break with elastic gate.

Water entry of decelerating spheres simulations using improved ISPH method

In this paper, we simulated the vertical impact of spheres on a water surface using three-dimensional incompressible smoothed particle hydrodynamics(3-D ISPH) method. The sphere motion is taken to be a rigid body motion and it is modeled by ISPH method. The governing equations are discretized and solved numerically using ISPH method. A stabilized incompressible SPH method by relaxing the density invariance condition is adopted. Here, we computed the motions of a rigid body by direct integration of the fluid pressure at the position of each particle on the body surface. The equations of translational and rotational motion were integrated in time domain to update the position of the rigid body at each time step. In this study, we improved the boundary treatment between fluid and fixed solid boundary by using virtual marker technique. In addition, an improved algorithm based on the virtual marker technique for the boundary particles is proposed to treat the moving boundary of the rigid body motion. The force exerted on the moving rigid boundary particles by the surrounding particles, is calculated by the SPH approximation at the virtual marker points. The applicability and efficiency of the current ISPH method are tested by comparison with reference experimental results.