The Propagation Characteristics Of Shock Wave In A Flat Confined Space

The characteristics of the shock wave and its shock wave propagation characteristics in the closed structure are much more complex than in the free air field,and the distribution of the load of the inner wall becomes more complicated.In the military construction and real life,there are a lot of flat structures,such as ship cabin,underground command post,underground defense place,underground car park and so on,one dimension of the flat structure is far smaller than the other two dimensions.The study of the propagation law of shock wave in the structure of this kind of structure will provide the theoretical basis for the calculation of the load distribution of the inner wall,and provide the reference for the design of the protection design,which has important theoretical research value and practical application value.In this paper,the propagation law of explosion shock wave and the distribution law of wall load in closed structure are analyzed by means of explosion experiment in flat rectangular device.Based on the explosion experiment,LS-DYNA software was used to simulate the explosion in the flat rectangular space under different working conditions.The experimental and numerical simulation results were analyzed qualitatively and quantitatively according to the shock wave propagation theory.The main contents and conclusions of this paper are as follows:(1)On the basis of the theory of shock wave propagation,the explosion test of flat rectangular confined space was carried out,and the overpressure time-history curve of each measuring point with different charge and charge position was obtained.Pressure-time curve is no longer a single peak pulse,but showed a multi-peak,the first peak is no longer the largest over-pressure,with a periodic macro-pulsating phenomenon.In the corner and ridge near,the over-pressure decay slow and the role of time increased.At the same time,there is a pulse jump after a certain peak,showing a typical bimodal structure.As the upper and lower wall reflection enhancement,these points in the empirical formula estimation,there will be measured value is about 2 times the estimated value.(2)On the basis of experiment,using LS-DYNA software to simulate the implosion of explosives in the flat rectangular space,and reproduce the process of shock wave formation and reflection superposition and catch-up in confined space.The explosion test data were used to calibrate the simulation parameters,and the overpressure time-history curves of different measuring points at different charge positions were obtained.Based on the propagation of shock waves and the reflection superposition,the overpressure time-history curves of different measuring points are analyzed,and the effects of dose change and charge position on shock wave propagation are considered.The results show that the pressure of the shock wave does not decrease with the increase of the distance in some paths,but the incident pressure decreases first and then increases.The overpressure curve of some measuring points also appeared a double-peak structure with short time interval.The double-peak structure disappears with increasing distance.For the points near the ridge,the shock wave is more prone to superposition and convergence due to the constraints of multiple walls,so that the shock wave overpressure propagation attenuation of the same distance after a smaller amplitude.When the charge position changes,especially when the explosives are exploded at the corners,the incident overpressure at the same dose will be several times larger than at the other detonation positions when the shock wave propagates to the same distance measuring point.It is found that the shock wave will gradually catch up with the incident shock wave due to the reflection enhancement of the upper and lower wall,and then undergo a dynamic transcendence and equilibrium after the shock wave propagates in the whole flat structure,and the latter is approximated by the plane wave spread.(3)The theoretical analysis of the shock wave propagation of the flat structure is carried out.Combining with the experimental and numerical simulation results,it is determined that the growth mechanism of the shock wave in the propagation process is the superposition mechanism of the Mach reflections of the upper and lower walls,and the superposition theory of the shock wave Mach theory in the flat structure is established.The results are in good agreement with the experimental and numerical simulations.