Abstract
Results of numerical simulations of explosion events greatly depend on the mesh size. Since these simulations demand large amounts of processing time, it is necessary to identify an optimal mesh size that will speed up the calculation and give adequate results. To obtain optimal mesh sizes for further large-scale numerical simulations of blast wave interactions with overpasses, mesh size convergence tests were conducted for incident and reflected blast waves for close range bursts (up to 5 m). Ansys Autodyn hydrocode software was used for blast modelling in axisymmetric environment for incident pressures and in a 3D environment for reflected pressures. In the axisymmetric environment only the blast wave propagation through the air was considered, and in 3D environment blast wave interaction and reflection of a rigid surface were considered. Analysis showed that numerical results greatly depend on the mesh size and Richardson extrapolation was used for extrapolating optimal mesh size for considered blast scenarios.
Highlights
Today’s global society faces many challenges that have not been present before
The purpose of this paper is to offer guidelines for selection of appropriate air mesh size
Two scenarios were considered for the purpose of further clarifying the influence of air mesh size on simulation results and enabling further development of blast loading analysis
Summary
Today’s global society faces many challenges that have not been present before. are military facilities exposed to terrorist threats, and many civilian buildings and structures are in danger. Chapman et al [4] conducted a comprehensive parametric study of model grid size to obtain optimal mesh size as a part of their research on the use of Autodyn 2D for simulation of blast wave interaction with structures Their results were compared to those from existing simple experimental tests, and they concluded that Autodyn 2D is a suitable tool for blast wave investigation. This is a clear indicator that a numerical mesh size convergence test needs to be carried out prior to large-scale numerical simulations With respect to these results and recommendations, for the purpose of this research, it was necessary to determine the amount of explosive which is likely to be placed under the overpass. Physical characteristics of vehicles, which dictate the shape, and confinement of the charge, detonation point, and consequent flying debris (fragmentation) are not taken into consideration, and only transport capacity was used in order to estimate the amount of explosive
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