Visualization of Shock Wave by Electric Discharge

Abstract

Theme O PTICAL systems such as schlieren systems, MachZehnder interferometers, and shadowgraphs have been used as typical methods to observe shock waves around models. However, any shock shape cannot necessarily be observed by these optical systems. For instance, it is difficult to measure a cross-section of a shock wave around a model, especially that around a winged body as shown in Fig. 1. In this case the shock shape in the shaded region (dotted line) cannot be observed by any optical method, because a part of the optical axes is intercepted by the body. In this paper, an observing method of shock waves by using an electric discharge has been tried. The principle of the method is based on the fact that a radiation intensity of an electric discharge depends on gas densities. When an electric discharge is generated across a shock wave, the radiation intensity in the shock layer is different from that in the freestream according to the difference of each density, consequently the location of the shock wave can be easily found by taking a photograph of this discharge column. Since the location of the electrodes may be chosen arbitrarily and the discharge column can be observed from any direction, it will be expected to be able to observe cross-sectional shock shapes or the shock wave in a shaded region as stated above. W I N G E D BODY