High-intensity air-explosion-induced shock loading of structures: consideration of a real gas in modelling a nonlinear compressible medium

Abstract

The existing practice of designing air-blast-resistant structures relies on the ideal gas model. But this model predicts the maximum value of the reflection coefficient (ratio of the reflected to the incident pressure) to be 8, whereas it can go up to 20 or more as reported in the literature. To address this discrepancy, air medium is modelled as a real gas instead of an ideal gas, where the effect of intermolecular forces, vibration, dissociation, electronic excitation and ionization are included. Ranges of peak over-pressure are identified where the ideal gas assumption cannot be used. Differences in impulse transmitted to the free-standing plates of different mass owing to relaxing of the ideal gas assumption and consideration of the real gas model are evaluated. Impulse transmitted to the structures for constant and variable back pressure (VBP) is also compared considering the real gas model. The result shows that for high-intensity shock, the ideal gas model under-predicts impulse transmitted to heavy plates but over-predicts the same for light-weight plates. Impulse transmitted to light-weight plates is also overestimated if VBP is neglected. The implications of this research are substantial for designing high-intensity air-blast mitigating structures, which if not considered properly, may lead to compromise in structural performance.