Narrow Results

A numerical simulation of penetration/perforation process of a concrete slab by a cylindrical steel projectile using the Smoothed Particle Hydrodynamics (SPH) method is studied in the paper. In the simulation, the available hydrocode AUTODYN2D is employed with the improved RHT concrete model, in which a Unified Twin-Shear Strength (UTSS) criterion is adopted in defining the material strength effects, and constructed a dynamic multifold limit/failure surfaces including elastic limit surface, failure surface and residual failure surface. The proposed model is incorporated into the AUTODYN hydrocode via the user defined subroutine function. The results obtained from the numerical simulation are compared with available experimental ones. Good agreement is observed. It demonstrates that the proposed model can be used to predict not only the damage areas and velocity reduction of the projectile during the perforation process but also the debris clouds of spalling process.

Waves play a very important role in the mixing process of oil slick, and greatly affect the distribution of oil pollutants in the water column near sea surface. In this study, the mixing process of spilled oil under breaking waves is simulated by using a multiphase SPH-based model. The model is an extension of our previous model. Modifications for two-phase flow are introduced to solve the instability problems caused by the high density ratio at interfaces. The surface tension between two fluids is also included in the multiphase model. The model is tested by simulating the deformation of an initially square droplet in another fluid due to surface tension, which is a classic problem usually used to test the two-phase flow model. The density ratio between the two fluids has been set to be 1/1000. The results show that the new set of SPH formulations can well deal with the large density difference at the interface of two fluids. And then it is applied to simulate wave breaking where the water surface is covered by a layer of oil. The mixing process of surface oil slick in water column is demonstrated.

The paper presents a weakly compressible Smoothed Particle Hydrodynamics (SPH) model to investigate the wave breaking of coastal slope. The SPH method is a mesh-free Lagrangian approach which is capable of tracking the large deformations of the free surface with good accuracy. To verify this numerical simulation, three different types of wave breaking, namely, spilling, plunging and surging breaking are successfully simulated. The computations are validated against the experimental data and a good agreement is observed. The velocity and pressure distributions are analyzed and visualized. The turbulent transport mechanism including vorticity and turbulent kinetic energy on the simulation results are also investigated in further detail. The SPH modeling is shown to provide a promising tool to predict the breaking characteristics of different waves.