Determination of pulsed-source cloud size/rise information using high-speed low-speed and digitized-video photography techniques

摘要

per discusses a laboratory method based on generating a buoyant thermal cloud through explosively bursting an aluminum foil by a rapid electric discharge procedure. The required electric energy is stored in a bank of capacitors and is discharged into the foil through a trigger circuit on external command. The aluminum first vaporizes and becomes an aluminum gas plasma at high temperature (approximately 8000 K) which then mixes with the surrounding air and ignites. The cloud containing these hot combustion products rises up in an unstratified anechoic environment. As the cloud rises, it entrains the air from the surroundings due to turbulent mixing and it grows. To characterize this cloud rise, three different types of photographic techniques are used. They are: high-speed photography (6000 fps), low-speed photography (200 fps), and video photography (30 fps). These techniques cover various time scales in foil firing schedule beginning from early time (up to 10 msec) to late time (up to 4 secs). Images obtained by video photography technique have been processed into a digital format. In digitizing the video tape data, an optical video disk player/recorder was used together with pc-based frame grabber hardware. A simple software routine was developed to obtain cloud size/rise data based on an edge detection technique.