Wednesday  |  Monongahela  |  03:10 PM–03:30 PM

#13597, Experimental Investigation of Regular to Irregular Shock Reflection Transitions in 2D and 3D

Shock waves can undergo either regular or irregular reflections, but theory and experimental results do not always agree. Understanding the transition criteria between regular and irregular reflections is critical as the type of reflection greatly changes the properties behind the shock front. For example, understanding what parameters cause these different reflections and what the changes in shock properties are will allow for greater control of shock focusing events. Extreme conditions, including pressure, temperature and density, exist in the focal region where multiple shocks coalesce. Depending on the situation, this can be beneficial or harmful. The ability to control the shock focusing process could aid in improving existing technology such as shock wave lithotripsy.

Experimental parameter studies of shock-shock and shock-structure interactions were carried out using an exploding wire system (EWS). The EWS consists of four 50kV capacitors set up in parallel, and a high-voltage power supply. When signaled, the stored energy is quickly released through thin wires, which vaporizes them and creates shock waves, effectively creating a miniature explosion. The EWS allows for a fast turnaround between experiments and therefore it is less expensive and time consuming than performing computational simulations for multiple shock waves. For these experiments, multiple wires were arranged in various patterns such that a converging shock wave was produced after the wire explosions. Schlieren imaging and ultra-high-speed photography were used to visualize the shock wave focusing event. In addition, pressure sensors were used to detect local pressure changes.

Schlieren photographs were analyzed using Matlab to precisely track the shocks locations as functions of time to extract their radii. Mach numbers were calculated, and the resulting shock reflections were studied for different initial energy levels stored in the capacitor bank. These experiments were performed using a 2D test section, which creates cylindrical shocks, and was then repeated using a 3D test section to create spherical shock waves. Criteria to predict when a regular reflection transitions to an irregular reflection were determined for the cylindrical and spherical cases. The results were then compared to transition criteria available in literature for shock waves with constant flow conditions behind them.

Grace Rabinowitz   Colorado School of Mines
Finnigan Wilson   Colorado School of Mines
Kadyn Tucker   Southern Utah University
Michael Oliver   Colorado School of Mines
Jacob Golson   Colorado School of Mines
Michala Lee   Colorado School of Mines
Rodrigo Chavez Morales   Colorado School of Mines
Veronica Eliasson   Colorado School of Mines