Abstract
The blast wave caused by the explosion of the explosive and so on shows the refractive index which is different from that of ambience because the wave is accompanied by the density change of the medium. The Schlieren method is often used as a technique to observe the behavior of fluid using the difference of refractive index. However, it is difficult to apply to outdoor experiments because the method requires arrangements of some optical equipments around the subject. In this study, the visualization of the blast wave in a convenient method from the digital frame images which had been taken by a digital high-speed camera in a past outdoor experiment without any optical equipment was tested. This method was a subtraction of images, and a processed image was produced by difference of gradations between two original frame images before and after the explosion. In a part of the background which resulted in a mottled pattern having minute bright and dark parts, the blast wave was possible to be visualized in every frame image. The main blast wave and reflected blast wave from the ground were observed in the processed images. The equivalent ratio to other conventional explosives was derived from the propagation of the blast wave clarified by the processed images. Consequently, this method can be used for estimation of the power of explosion.
