Hazard Source Characterization and Propagation II: Fragments

Abstract

The chapter presents a hazard propagation model for solid objects. A basic approach to describe the fragment and debris launch and distribution in case of explosive events is given, which is often only based on experimental data. It offers the opportunity to (geo-) locate three-dimensional threat trajectories in space. A little similar approaches are of interest when tracing the dispersion of solid agents or fluids. The assumptions of the presented approach are given. In particular, it is not valid for the near field. The chapter shows how a sufficient hazard source description relates to the hazard propagation modeling: the former should contain sufficient information for the later. However, it is not show in detail how the fragment launch conditions are obtained experimentally, by analytical-empirical models or by computational continuum-mechanical simulation. The modeling and visualization of hazards requires the use of natural coordinate systems: the coordinate system for the hazard source, coordinate systems for objects in the surroundings of the hazard source, for the visualization of earth’s surface and for modeling the forces on earth’s surface that influence the hazard propagation. The chapter presents a minimum of such coordinate systems and how they are transformed to each other. For describing the physics of the propagation, geometry properties of the objects propagating and the properties of the medium they are propagating through are necessary to determine the physical forces acting on the propagating objects. The given definitions of various hazard densities of explosions are an example of quantifying parameters for representing the time-dependent 3D hazard field on a surface of interest. It is carefully distinguished between the representation of the hazard potential and its interpretation in terms of potential damage. The chapter also illustrates that computational simulation and its visualization are a powerful tool to model the propagation of hazards, in particular also allowing to take account of the scenario geometry, e.g. of barriers close to the hazard source or close to objects at risk.