Influence of non-stationarity of the hydrodynamic process on an emergency situation development

Purpose. The article examines the influence of effects associated with the rapidity of explosive phenomena or their non-stationarity on the main parameters, which characterize an explosion. In particular, the influence of development of a jet flow from a discharge breach released during an explosion on the levels of explosive pressure in an emergency room is investigated. Scientific and regulatory sources assume that the outflow of gases that provide for the release of explosive pressure in a room during an internal emergency explosion occurs in accordance with the correlation valid for stationary flows. The authors show that the given approach is valid for a limited class of explosive phenomena. When using blast-relief structures (BRS), the process of forming a submerged jet has a significant effect on the levels of blast pressure in a room protected from explosion loading. Methods. When substantiating the need to take into account the influence of the a submerged jet formation process (the effect of non-stationarity of an explosive accident development process) on the levels of blast pressure in a room equipped with a BRS, numerical methods based on the general equations of gas dynamics were used. The difference schemes approximating the conservation equations are based on the well-known Godunov method, which allows describing non-stationary gas-dynamic problems. The results of numerical calculations were used to adjust the system of differential equations describing dynamic loads in rooms equipped with BRS, which were obtained under the assumption that the process of explosion loading formation occurs in a quasi-static mode. In this mode, it is assumed that the blast pressure in the room depends on time only and does not depend on the spatial coordinate. Findings. The calculations performed showed that when the BRS is opened, the forming drowned jet has a significant effect on the maximum level of blast pressure in the room. This phenomenon must be taken into account when developing explosion-relief waste valves that must ensure acceptable (permissible) levels of blast pressure. Research application field. The results of the study should be used in the development of BRSs applied in premises with explosive technologies to ensure the blast resistance of buildings. Conclusions. This article shows that when calculating the parameters of explosion loading in rooms equipped with BRS, it is necessary to take into account the non-stationarity of the forming drowned jet. The presented justifications are based on a series of numerical calculations performed using difference schemes based on conservation equations written in integral form, which allows describing non-stationary gas-dynamic phenomena. The results of full-scale experiments are presented, confirming the need to take into account the effect of non-stationarity when developing BRSs that ensure explosion resistance of buildings and premises.