A topical and challenging area is concerned

A topical and challenging area is concerned with the prediction of the effects of blast waves generated by energetic and non-energetic sources. Modern conflicts are increasingly characterised by asymmetric urban warfare with improvised explosive devices (IEDs) often playing a tachykinin role on the one hand and an armed forces requirement for minimal collateral effects from their weapons on the other. These are areas of active research, for example References [5,6]. In addition, a significant amount of research has been undertaken over recent years to describe and predict the complex blast loading due to buried mines [7,8]. Many of the developments in GRIM have been driven by these requirements to provide an accurate description of blast in a wide range of scenarios. This has included the physics and chemistry of an energetic material that can be exploited to enhance the blast field [9,10]. Although the numerical scheme in GRIM is second order accurate and the advection step is third order accurate in regions of smooth flow, the inherent numerical dissipation results in reduced accuracy in the far field. Reduction of the mesh resolution can alleviate this problem; however, a 1 mm mesh resolution in a 4 m3 simulation space equates to a 64 billion cell problem. Realistically sized problems that contain objects, e.g. a vehicle subjected to an IED attack, rapidly become intractable, especially with the need to properly resolve the vehicle to correctly reproduce the details of the flow field around it and reproduce any localised regions of blast enhancement. Whilst methods that link GRIM with DYNA to describe blast effects on and within structures, and the gross features of the response have been very successful [11], the increasing scale of the problems has shown the details of the response to be less well described.
EAGLE The EAGLE code has been designed and developed from scratch allowing for efficient implementation of up-to-date algorithms to meet the challenging requirement to simulate a wide range of problems, each potentially requiring a different combination of physical processes. These might include fluid-dynamics, solid material strength, reaction chemistry, moving boundaries or material fracture, amongst others. For C value reason, the code has been designed in a highly modular fashion, such that individual physics modules can be “plugged-in” to the simulation depending on the client\'s application. This is shown schematically in Fig. 1. Traditionally, numerical methods in solving such multi-material problems have used Lagrangian, mixed Eulerian–Lagrangian (ALE), or smooth particle hydrodynamics (SPH) approaches [12–14]. Recent advances in numerical methods for coupling CFD (Computational Fluid Dynamics) and CMD (Computational Material Dynamics) algorithms have made such coupled simulations possible in the Eulerian frame of reference [15–17]. At the core of the EAGLE formulation is a model for the description of fluid dynamics (Navier–Stokes equations), which is (two-way) coupled to an elastic–plastic model for the description of material dynamics. The Riemann ghost-fluid method is employed to represent the evolving material interfaces as discontinuities on discrete space. The coupling between the materials at these interfaces is achieved by means of a new approximate mixed Riemann solver [17]. The mixed Riemann solvers are able to accommodate realistic equations of state (in Mie–Gruneisen form or from SESAME tables). Additional modules exist for additional physical and chemical processes such as reactive flow, fracture etc.
EAGLE-Blast The modularity of the EAGLE code has allowed the development of a derivative of EAGLE called EAGLE-Blast, which is a single material version tailored for blast simulations with the ability to include rigid bodies within the flow field. Similar capability is possible by setting appropriate initial and boundary conditions in commercial packages (such as those offered by ANSYS) or tailored software like ProSAir [18]. However, access to the source code (to gain knowledge of the underlying formulations and numerical methods as well as for continuous maintenance and upgrade) and confidentiality issues make an in-house code development essential. The resulting code has been optimised for maximum efficiency and computational speed. In this section, we summarise the EAGLE-Blast formulation and its numerical solution.