Effect of high altitude on the temperature propagation of typical explosives in tunnel wave fronts

Thermal effects are the primary means of damaging ammunition targets, and their impacts are particularly pronounced in enclosed environments. With the ongoing advancement of efficient damage technologies and the increasing complexity of future combat scenarios, it is crucial to evaluate weapon damage performance in high-altitude environments. Therefore, studying the propagation characteristics of explosion temperatures in high-altitude tunnels and developing a corresponding theoretical calculation model are of great significance for comprehensively assessing explosion damage under such conditions.

This study aimed to effectively characterize the propagation characteristics of the temperature at the blast wave front in long, straight tunnels with different types of condensed explosives at high altitudes. A multimaterial numerical calculation method was employed to investigate the propagation behavior of the blast wave front temperature in such tunnels. First, the two-dimensional axisymmetric numerical calculation method was validated by comparing the peak temperature data with the results of the existing explosion temperature field tests. Afterward, based on the above-described numerical calculation method, standard atmospheric parameters, and the existing explosive Jones-Wilkins-Lee(JWL) equation of state parameters, a numerical model is developed to simulate the explosion of different types of condensed explosives at high altitudes in a long straight tunnel. The model analyzes the explosion temperature field parameters, including the plane wave formation distance, peak temperature, shock wave front propagation velocity, and standard deviation of shock wave front arrival times. Finally, using the Hugoniot principle and Sachs dimensionless correction method, a mapping calculation model of the peak temperature and peak overpressure of the shock wave front in a typical high-altitude tunnel with condensed explosives is established, and the accuracy of the model is verified through numerical calculation results.

The results indicate that the plane wave formation distance increases gradually with both the elevation and internal energy per unit volume of the explosive. At an altitude of 4 000 m, the plane wave formation distance for the different types of condensed explosives increases by an average of 24.8% compared with that in a flat environment. At the same altitude, the plane wave formation distance increases by an average of 0.89 m/GPa with a rise in internal energy per unit volume of the explosive. As a result, the propagation velocity and average deviation of the shock wave front arrival time increases with the elevation and internal energy. This result reflects the complexity of the interaction between the shock wave front and tunnel wall, leading to a decrease in the flatness of the shock wave front. At an altitude of 4 000 m, the peak temperature of the shock wave front for different condensed explosives increases by an average of 27%. At the same altitude, the peak temperature of the shock wave front increases by an average of 0.013 k℃/GPa with the rise in internal energy per unit volume of the explosive. The peak temperature for different altitudes and explosive types exhibits a decreasing trend with the increase in propagation distance, with the rate of decrease also reducing. Under various altitude and explosive-type conditions, the deviation between the theoretical analysis model and numerical calculation results is < 10%, indicating good accuracy.

The results of this study provide a theoretical basis for understanding the temperature propagation of shock wave front explosions in condensed explosive tunnels under high-altitude conditions. They also offer guidance for weapon damage assessment and protection engineering design in high-altitude extreme combat environments.