Abstract

Within the category of improvised explosive devices are those that form explosively formed projectiles which penetrate armor and armored systems, such as those used by insurgents against allied forces in operational areas. The purpose of this study is to reproduce and understand the behavior of these improvised explosive devices capable of generating high-velocity, high penetration projectiles. Understanding their behavior will allow for improved knowledge about them, and thus will allow us to more effectively combat them. Thus, the corresponding tests were carried out and the results were obtained from the first characterizations of explosively formed projectiles built using traditional methods, just as a terrorist would have built them. Along with this, numerical models were created for each test simulating the entire event from beginning to impact on the target, including all the intermediate steps. There were three configurations tested and simulated using the software of finite element analysis, LS-DYNA®, a 2-D asymmetric configuration with Lagrangian meshes. The results obtained by the model were compared with data obtained in the experimental tests, yielding a high precision between simulated and tested data. With the data obtained in this study it can be concluded that the improvised explosive devices -explosively formed projectiles is a serious threat. Generated models will allow us to know more about these weapons, to reduce costs in the fight against the threat of improvised explosive devices-explosively formed projectiles and therefore against terrorism with explosively formed projectiles, and to have a holistic approach to the threat and to reduce the cost of experimentation. Minimize the experimental expense.

Abstract

In this work we extend the Particle Finite Element Method (PFEM) to multi-fluid flow problems with the aim of exploiting the fact that Lagrangian methods are specially well suited for tracking interfaces. We develop a numerical scheme able to deal with large jumps in the physical properties, included surface tension, and able to accurately represent all types of discontinuities in the flow variables. The scheme is based on decoupling the velocity and pressure variables through a pressure segregation method which takes into account the interface conditions. The interface is defined to be aligned with the moving mesh, so that it remains sharp along time, and pressure degrees of freedom are duplicated at the interface nodes to represent the discontinuity of this variable due to surface tension and variable viscosity. Furthermore, the mesh is refined in the vicinity of the interface to improve the accuracy and the efficiency of the computations. We apply the resulting scheme to the benchmark problem of a two-dimensional bubble rising in a liquid column presented in [[#cite-1|[1]]], and propose two breakup and coalescence problems to assess the ability of a multi-fluid code to model topology changes.

Abstract

In this work we extend the Particle Finite Element Method (PFEM) to multi-fluid flow problems with the aim of exploiting the fact that Lagrangian methods are specially well suited for tracking interfaces. We develop a numerical scheme able to deal with large jumps in the physical properties, included surface tension, and able to accurately represent all types of discontinuities in the flow variables. The scheme is based on decoupling the velocity and pressure variables through a pressure segregation method which takes into account the interface conditions. The interface is defined to be aligned with the moving mesh, so that it remains sharp along time, and pressure degrees of freedom are duplicated at the interface nodes to represent the discontinuity of this variable due to surface tension and variable viscosity. Furthermore, the mesh is refined in the vicinity of the interface to improve the accuracy and the efficiency of the computations. We apply the resulting scheme to the benchmark problem of a two-dimensional bubble rising in a liquid column presented in [1], and propose two breakup and coalescence problems to assess the ability of a multi-fluid code to model topology changes.