The control of underwater explosions is an industrial concern. In this paper, a comparison of experimental and numerical results of high-pressure generation using underwater explosion of spiral detonating cord is presented. To demonstrate that the converging process of underwater shock wave yields high pressure near the spiral center, the experimental investigation aims to compare underwater shock wave pressures obtained with several detonating cord geometrical configurations and study the wave converging process for a spiral cord. Because the experimental approach of these fast transient events is expensive and time-consuming, numerical simulations of experimental cases by using multi-material Eulerian formulation are carried out. The multi-material Eulerian, which is a particular multi-material ALE (Arbitrary Lagrangian Eulerian) formulation was successfully used in many industrial applications involving computational fluid dynamic problems. By using an explicit finite element method, a good agreement between numerical and experimental results will valid multi-material Eulerian formulation abilities to solve accurately underwater shock wave problems for spiral detonating cord in various shapes.

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The simulation of problems in continuum mechanics involving highly transient phenomena and large deformations such as blast, shock wave propagation and reflection presents significant challenges in computational mechanics. Several models have been developed which allow some visualization of blast propagation. In this article, the numerical tool used for the blast modeling is an Eulerian multi-material formulation. The multi-material formulation has already been used with success in the simulation of fluid with large motion such as the tank sloshing modeling or the simulation of metal cutting processes. This paper describes an air blast simulation with a multi-material Eulerian formulation implemented in an explicit finite elements code, LSDYNA3D. Experimental results give the pressure histories to a distance of 5 feets from the point of initial detonation of C4-explosive. A first purpose is to prove the ALE capabilities to correlate numerical results with the experimental results. An experimental pressure history at the same point is measured when the blast shock is reflected by a ground. The second aim of this paper is to compare the experimental pressure history and the numerical pressure history for the same point.

Fluid-structure interactions play an important role in many different types of real-world situations and industrial applications involving large structural deformation and material or geometric nonlinearities. Numerical problems due to element distortions limit the applicability of a Lagrangian description of motion when modeling large deformation processes. An alternative technique is the multi-material Eulerian formulation for which the material flows through a mesh, fixed in space and each element is allowed to contain a mixture of different materials. The method completely avoids element distortions and it can, through an Eulerian-Lagrangian coupling algorithm, be combined with a Lagrangian description of motion for parts of the model. The Eulerian formulation is not free from numerical problems. There are dissipation and dispersion problems associated with the flux of mass between elements. In addition, many elements might be needed for the Eulerian mesh to enclose the whole space where the material will be located during the simulated event. This is where the multi-material arbitrary Lagrangian-Eulerian (ALE) formulation has its advantages. By translating, rotating and deforming the multi-material mesh in a controlled way, the mass flux between elements can be minimized and the mesh size can be kept smaller than in an Eulerian model.

In order to realize numerical simulation of fast transient events, some wave propagation codes, which allow studying the time resolved development of shock wave propagation due to penetration, and detonation, were developed. In this article, Eulerian Multi-material and Arbitrary Lagrangian Eulerian formulations are used. Both formulations have already been used with success in the simulation of fluid with large motion such as the tank sloshing modeling, the overdriven detonation or the simulation of metal cutting processes. This article describes an air-blast simulation using an explicit finite elements code LS-DYNA. The main aim of this investigation is to compare numerical results with experimental results in order to prove the abilities of Eulerian Multi-Material and ALE formulations to treat air-blast problem using an explicit finite element method.