Numerical evaluation of afterburning parameters in partially confined TNT explosions informed by experiments

Abstract

Afterburning, which is the secondary combustion of detonation products with ambient oxygen, can substantially increase the energy released in confined TNT explosions. Predicting this phenomenon in partially confined environments is considerably more challenging than under ideal, fully confined conditions, yet it is essential for accurate estimation of internal blast loads. This study evaluates afterburning behavior in partially confined scenarios by correlating numerical simulations with experimental data. Numerical modeling is based on previously conducted experiments, serving as a database to assess the afterburning contribution in Viper::Blast CFD simulations. An engineering model is utilized to account for the combustion of fuel-rich detonation products, where the total energy release and characteristic duration are controlled by two key parameters. A theoretical framework is first introduced to estimate the maximum potential afterburning energy under full confinement for both oxygen-rich and oxygen-deficient conditions. Two scenarios are subsequently analyzed: fully confined and partially confined explosions. For the former, simulations show good agreement with published experimental data when the maximum theoretical energy is applied. For the latter, a comprehensive numerical study identifies the effective magnitude and timing of afterburning that best fits the tests, highlighting the significant influence of venting on energy release. Finally, an additional literature-based case study is simulated to further illustrate the effect of venting. The analysis emphasizes the caution required when extrapolating these parameters to different confinement or venting conditions and underscores the need for further experimental and numerical investigation.