In our efforts to push the boundaries of flow visualization I look to the sound barrier. The beauty of this image lies in the natural phenomena that is occurring, breaking the sound barrier. This image uses Schlieren imaging to depict shock waves. Schlieren imaging allows us to photograph the flow of fluids of varying density. To be able to even reach super sonic speeds is a great scientific feat itself, and to be able to photograph and analyze it at this level is even more so. Understanding the forces at play here and being able to visualize them shows us beauty in modern day aviation and imaging. In this image we can clearly see different air density gradients. This technology allows us to research the possibility of a quiet yet very high-speed aircraft.
Image Link: http://www.nasa.gov/centers/armstrong/features/bosco.html
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Nice photo David. The terms “sound barrier” and “break the sound barrier”, which we still use today, highlight how much progress has been made in the last 70 years in our understanding of aircraft flight and the science of fluid dynamics. Before Chuck Yeager’s flight on Oct 14, 1947 there was much debate in the aerodynamic and thermodynamic community as to whether an aircraft could even survive a flight that fast. Some suggested that compressible effects at the speed of sound would create a “barrier” like hitting a wall that would completely destroy the aircraft. Chuck Yeager was therefore a brave man to climb into the X-1 to attempt this feat when some great minds in the years before has predicted he’d be killed (he’s even braver for doing it with a broken rib from being thrown off a horse the day before, a detail he failed to mention to his superiors before the flight). When he achieved his historic flight he was said to have “broken the sound barrier” which in actual fact was never really there. What he did was such a nationally celebrated huge event that the term “break the sound barrier” has become irrevocably ingrained in our language even though the antiquated term is as scientifically correct as calling the world flat.
I believe this image is an example of a relatively new form of Schlieren photography called Background Oriented Schlieren, BOS (classical Schlieren techniques have been around for a long time). BOS is possible these days due to improved image processing capability provided by fast computers and GPUs. If you’re interested on the details of this technique NASA has a nice explanation with some more cool photos:
http://www.nasa.gov/centers/armstrong/features/shock_and_awesome.html