Automated extraction of interface perturbations from explosively driven gas clouds in varying confinement *

The gas cloud produced by a Winchester 209 primer is characterized by an explosive expansion of gases forming a jet outward from the primer. The gas cloud mixing produced by impinging this jet on an acrylic plate with a confined expansion volume is studied using high speed refractive imaging axially along the primer. Schlieren imaging allows the identification of the interface between the explosive product gases and the surrounding air. The interface location is extracted using automated morphological image processing techniques. The automated techniques are validated against a manual tracking of the interface, and good agreement is found. Using quarter symmetry, a dominant frequency and wavelength for the perturbations on the gas cloud interface is extracted using FFTs. The confinement of the expanding gas cloud is varied by increasing the space between acrylic plates. The evolution of the dominant wavelengths with confinement variation and time is tracked. Comparisons are drawn to existing experimental and theoretical literature on the evolution of the mixing region at the interface for both radius and wavelength with respect to time.