August Toepler — The first who visualized shock waves

Abstract

Abstract. The scientific investigation of the nature of shock waves started 130 years ago with the advent of the schlieren method which was developed in the period 1859-1864 by August Toepler. At the very beginning applied to the visualization of heat and flow phenomena, he immediately turned to air shock waves generated by electric sparks, and subjectively studied the propagation, reflection and refraction of shock waves. His new delay circuit in the microsecond time regime for the first time made it possible to vary electrically the delay time between a spark generating a shock wave and a second spark acting as a flash light source in his schlieren setup. In 1870 Toepler, together with Boltzmann, applied Jamin's interferometric refractometer and extended the visualization to very weak sound waves at the threshold of hearing. Toepler's pioneering schlieren method stimulated Ernst Mach and his team to objectively investigate the nature of shock waves: they improved Toepler's time delay circuit; continued the study on the reflection of shock waves; introduced shadowgraphy as a modification of the schlieren method; photographed the propagation of shock waves generated by an electric spark and by supersonic projectiles, and improved interferometry. Based on a large number of original documents the paper illuminates the concomitant circumstances of the invention of the schlieren method and its first applications by others.

A time-resolved imaging and electrical study on a high current atmospheric pressure spark discharge

“…Such fast growth of the plasma channel, together with the inherent change in temperature and gas pressure induces a shockwave. 32 The supersonic expansion was confirmed directly, for all but one cases used in this work, since the characteristic shockwave sound was clearly audible during sparking. One can add that the gas temperature in the gap before the spark may be higher than room temperature as a result of earlier spark events.…”

Effects of Biofuel and Variant Ambient Pressure on FlameDevelopment and Emissions of Gasoline Engine.

“…Nevertheless, this method can be conducted by high speed camera and it is a visual process that used photograph to analysis. August Toepler [16], a German physicist in 1864 were developed this technology to study supersonic motion which widely used in aeronautical engineering to snap photograph of air flow around objects. Schlieren photography method was also used to observe the fluid evaporation and mixture formation in engine [15].…”

“…Moreover, the experimental method used to evaluate the detail of mixture formation process is schlieren optical visualization method. The basic principle of this technique is to combine the optical projection of an object with an indication of its light deflection [14][15][16].…”

High-speed visualization, a powerful diagnostic tool for microactuators - retrospect and prospect

“…The instrumental problems of illumination at high-speed photomicrography have already been addressed recently [15]. Since all high-intensity flash light sources have to be fed via high pulsed current, it requires a very careful shielding and grounding of the driving generator to prevent any detrimental electromagnetic interfering with the sensitive electronic camera, interconnected memories and the PC workstation.…”

“…Cine photomicrography, also called cinemicrography, evolved as early as 1894 from the first motion pictures of biological microdynamic events using a hardcranked microscope-coupled camera [9]. Review articles on cinemicrography predominantly cover the use of mechanical cine cameras [4,[10][11][12][13][14], but also address the important problem of microscopic illumination which again becomes important in electronic recording at ultra-high speed [15]. The development of mechanical cameras continued up to the late 1980s and finally culminated in sophisticated ultra-fast rotating-mirror framing cameras [16] with extreme framing rates up to 2.5;107 fps.…”