The paper summarizes the results of a study aimed at internal and external shock waves interactions with rigid and flexible obstacles in various compressible media (air, soil, metallic foam).
The problems of internal shock waves interaction aim at investigation of an interior explosion within a room with limited or no venting. This scenario may be the result of an ammunition storage explosion, or an explosive charge explosion as part of a terrorist action or a warhead explosion following its penetration into a closed space in a military action. An effective simplified model with lumped parameters based on the Bernoulli equation has been developed for the quasi-stationary phase of the detonation products outflow from the room through the venting openings. The initial internal gas pressure induced by the very short non-stationary phase is predicted by the developed approximate analytical formula, based on the full energy conservation law. The formula yields very good agreement with experimental data and with numerical analysis results. A comparison was performed between the test results, numerical results and the UFC 3-340-02, 2014 model. It was demonstrated that the developed simplified approach is well suited for simulation of the quasi-stationary phase of partially confined explosions and properly describes the pressure relief and gas outflow from the vented room.
A similar effective simplified model with lumped parameters of explosion venting due to separation of the protective cover has been developed. The proposed approach is demonstrated by the simulation of gas outflow from a chamber upon a sudden separation of the cover or upon a rectangular shutter rotation about a fixed line hinge. The analysis has been performed using the developed simplified approach and through simulations with AUTODYN. A good correspondence between both methods has been obtained.
The external shock waves interaction problems aim at investigation of shock waves propagation in an irreversibly compressible layered medium and their interaction with planar rigid and flexible obstacles or inclusions. The approach allows taking into account the irreversible bulk compaction of the soil medium and is based on the relationships of the shock and rarefaction waves. It reduces the medium-obstacle contact problem to the self-similar symmetric Riemann problem which widely used in analytical, semi-analytical and numerical methods of simulation of impact and shock problems in compressible media.
The Riemann problem for an irreversibly compressible medium has been solved. Its solution for a three-phase soil as well as for a metal foam medium is obtained. The solution introduces the maximum medium permanent density that is attained in the process of active loading. The possible wave configurations have been analyzed and the corresponding equations for the evaluation of the contact pressure and velocity have been obtained. The existence and uniqueness of the solution has been proven. Examples of the Riemann problem solution for various wave configurations show that neglecting the bulk elastic plastic deformations yields significant errors in the results both quantitatively and qualitatively. The proposed approach is demonstrated in the solution of P-wave attenuation in rock layered medium, in the solution of shock wave propagation in three-phase soil as well as in porous metal foam described as a two-phase medium. The effect of the air volumetric content in a porous medium on the possible wave configurations is investigated. The solution of the problem of a shock wave reflection from a rigid planner obstacle is obtained and the non-monotonic behavior of the reflection coefficient is discussed.
