Schlieren cinematography of shock-wave reverberation in interior spaces

Penn State's Full-Scale Schlieren Facility and a high-speed drum camera are used to investigate shock-wave phenomena from explosions within structures pertinent to aviation security issues. About 300 photographic frames are obtained at 30,000 frames/sec, allowing the complete period of relevant wave motion to be imaged. These frames can be assembled to create a short 'movie' of the event. The 2x3 m size of the schlieren field-of-view enables tests to be conducted at or near full-scale. A small balloon containing an oxygen-acetylene gas mixture produces an explosion with an initial shock strength of Mach 1.2, more than sufficient to reveal shock motion but not strong enough to do actual damage. Blasts at various positions in a 1.9 m square box have been observed as 'building blocks' of the complicated reverberation that occurs inside an enclosed space, as well as to validate computational DSMC predictions. The optical results are compared with shock overpressure measurements at the box walls. These results provide some insight into shock reverberation and the means by which blast energy is directed inside a structure. Supported by FAA Grant 99-G-032.