The modeling of explosion consequences traditionally focuses mainly on estimating blast damage. In order to produce realistic results, a numerical model of the blast wave propagation phenomenon must rely on judiciously chosen equation of state (EOS). The usage of the Jones-Wilkins-Lee (JWL) EOS for this purpose is quite ubiquitous. However, when the detonation products carry a hazardous material, a numerical model may be required to predict reliably the scattering of detonation products in addition to describing blast wave`s propagation. A possible relevant scenario may be an explosion in an enclosed space with detonation products emanating to the atmosphere through an opening in the enclosure like a door or a window in a room. In this particular instance, the usage of the JWL EOS may lead to insufficiently accurate results. The origins of this difficulty are discussed in this paper.
The JWL EOS was designed and calibrated for the high pressure range. Also, one of its characteristics is that the energy (temperature) dependence is identical to one of the ideal gas EOS. Furthermore, the JWL EOS reduces quickly, when pressure decreases, to a simple description of an ideal gas. The latter is valid only in the lower pressure range, lacking a proper description of the mid-range pressure regime. In contrast, the Becker-Kistiakowski-Wilson (BKW) EOS designed and calibrated for the mid-pressure range. This regime seems to be a particular relevance for the adequate modeling of the detonation products expansion. A preliminary study that was performed to describe numerically the evolution in time of the TNT explosion revealed differences in the results, especially for the gas products expansion, between the models using BKW EOS and JWL EOS. As a naïve attempt to create a "general purpose" model, one may start a simulation with the JWL EOS to describe the high pressure range and continue with the BKW EOS to describe the evolving shock wave as the pressure decreases below a certain threshold. The correct overall description of the process should include a continuous and smooth unification of the two equations of state, which were separately calibrated. In this study we will further examine the differences between the JWL EOS and BKW EOS, and explore possibilities to combine the two equations of state into a single one.
