Shock Wave Propagation Process Research Articles

OS1718 高速飛翔体衝突における衝撃波光学可視化計測

This paper reports the preliminarily experimental results of shock wave propagation visualization by hypervelocity impact. An experimental investigation of hypervelocity impact was performed by using a ballistic range at Institute of Fluid Science, Tohoku University. The process of shock wave propagation by hypervelocity impact was visualized by shadowgraph method and recorded by high-speed video camera.

Study on Influence Scope of Shock Wave and Smoke Flow after Gas Explosion

Gas explosion is very disastrous accident all over the world. Influence scope analysis of shock wave and smoke after gas explosion is of great importance and significance. The results indicate that, during the process of shock wave propagation destroying the air throttle, the shock wave energy will be consumed as part of air throttle destruction, which causes the overpressure reduced. However, the shock wave continues to be propagated and attenuated to a certain distance. Results on analyzing influence scope of smoke flow show that the smoke temperature and concentration in roadway are higher before restoring ventilation. The smoke is diluted by the fresh air through diffusion. After restoring ventilation, the temperature and concentration of smoke flow are lowered greatly. In conclusion, the influence scope study of shock and smoke flow is of full practice.

Experimental Investigation of a Novel Blast Wave Mitigation Device

A novel blast wave mitigation device was investigated experimentally in this paper. The device consists of a piston-cylinder assembly. A shock wave is induced within the cylinder when a blast wave impacts on the piston. The shock wave propagates inside the device and is reflected repeatedly. The shock wave propagation process inside the device lengthens the duration of the force on the base of the device to several orders of magnitude of the duration of the blast wave, while it decreases the maximum pressure over an order of magnitude. Two types of experiments were carried out to study the blast wave mitigation device. The first type of experiments was done with honeycomb structures protected by the blast wave mitigation device. Experimental results show that the device can adequately protect the honeycomb structure. A second type of experiments was done using a Hopkinson bar to measure the pressure transmitted through the blast wave mitigation device. The experimental results agree well with results from a theoretical model.

Basic study on promotion of thawing frozen soil by shock loading

The aim of study is to confirm a new technique that can crush the frozen soil and/or ice block using underwater shock wave generated by the underwater explosion of explosive. This technique can lead to the earlier sowing, which can have the larger harvest because the duration of sunshine increases. Especially, in Hokkaido prefecture, Japan, if the sowing is carried out in April, we can expect to have 150% of harvest in the ordinary season. In the case of small processing area such as road repairing, frozen soil is thawed by using the heat of gas burner and/or the electric heater. It is not a suitable plan to apply these heating methods to agriculture, from the point of view enormous amount of processing area. Thawing technique for frozen soil is effective against the cold regions, for example, Russia, Norway, and Sweden, etc. At first, we carried out experiments using a detonating fuse and ice block. The propagation process of shock wave into the ice block was observed by means of a high-speed camera. In order to check about that influence we tried to give an actual frozen soil a shock wave. We could get a result that existence of water layer serves an important role in promotion of thawing by the shock loading to the frozen soil.

Numerical investigation of unsteady shock waves in vapor-gas-droplet mixtures

The results of mathematical modeling of the evolution of unsteady shock waves in two-phase mixtures of inert gas, vapor and suspended liquid droplets with allowance for dynamic, thermal and mass phase interaction processes are presented. The influence of interphase mass transfer effects (droplet breakdown and evaporation, vapor condensation) on the structure of unsteady shock waves in vapor-gas-droplet mixtures is analyzed. The important influence of phase mass transfer and, in particular, droplet breakdown as a result of surface layer stripping by the gas flow on the distribution of the parameters of the carrier and dispersed components of the mixture behind the shock front is demonstrated. The effect of the principal governing parameters of the two-phase mixture on the unsteady shock wave propagation process is analyzed.

Gas Dynamics of Explosions

The subject of the gas dynamics of explosions is important for the under­ standing of various natural phenomena and for practical applications. In the processes of explosions of various explosive materials, cosmic explosions, and electrical discharges, complex gas motions behind shock waves arise. These gas motions can be studied experimentally, by means of models, or theo­ retically, i .e. , by means of the investigation of mathematical problems using equations of gas dynamics. In this paper only the theoretical questions will be considered. The data of observations and experiments will be used only for the illustration of the theoretical conclusions. To avoid details of the blast origin we shall use, as a rule, the conception of the point explosion. We con­ sider here such relatively new questions for gas dynamics as the influence of electromagnetic fields and chemical reactions on the process of shock-wave propagation. The theory of explosions includes two main topics: (a) the propagation of blast waves in unbounded media; (b) the interaction of blast waves with different obstacles and shocks. We shall study the questions of the develop­ ment of the blast in unbounded media only and shall n� ' t consider the prob­ lems of reflection and diffraction of shock waves. The list of cited literature includes works published before July 1970, and does not pretend to be complete. Also, the problems discussed are those of particular interest to the author.