Shock Front Instabilities in Conical Waveguides

A new shock front instability is described in converging conical waveguides designed to generate high shock velocity, temperature, and jetting along the central cone axis. In these systems, a classical Mach stem is developed inside the cone. As the Mach stem grows, rotational flow is generated behind the wave front due to the no-slip boundary condition and differential wave velocity within the cone. For certain shock speeds and densities, shock compression at the triple point will condense the matter to the extent that the rotational flow affects the shock front itself. When this occurs, the triple point will expand into a new Mach stem which is bisected by opposing rotational regions. A high speed Schlieren setup with high power pulse laser backlight is utilized to overshadow the blackbody generated by the shock and visualize the phenomena, as well as to validate hydrocode models. In this work, the instability formation criterion is described as a function of the initial working fluid density and shock velocity.