Page 29 - January 2006

Exposition, Vol. 3, Paper IMECE2003-55346 (ASME, New York, 2003).
Appendix: Highlights of some of the ISBF presentations
• Halvor Hobaek presented a paper with co-authors Adne Voll, Rune Fardal and Lucio Calise from the University of Bergen, Norway on laboratory scale model experiments for sound propa- gation in the atmosphere from 15 km to ground level. They were able to achieve a stable linear sound speed profile in a water tank by carefully mixing ethanol and water. Perhaps, surprisingly, it was found the laboratory mixture of ethanol and water made a sound speed profile which was quite stable over a period of sever- al months. Propagation of sound in this profile was examined and will be continued in the future. This work is part of the SOBER project, a SOnic Boom European Research project.
• Francois Coulouvrat provided a summary of his recent work with Reinhard Blumrich and Dietrich Heimann, also funded by the SOBER project. Their work has shown the critical importance of meteorology (weather) on the variability of sonic booms received on the ground. Their work has shown that during supersonic cruise, weather changes the peak pressure only +/- 10 percent, but that lateral variability to either side of the flight track can be quite substantial. They have also shown that there can be meas- urable changes in booms received on the ground due to the sea- son of the year and the time of day or night. Further their work has shown the importance of understanding the focusing of sonic boom, called a superboom, when an aircraft is accelerating up to cruise speed. The meteorology seems to have a substantial impact on the strength of such superbooms.
• Osama Kandil of Old Dominion University described his recent work with Xudong Zheng to model the nonlinear Tricomi equa- tion to predict superbooms for a variety of different shaped sonic booms. Their results compared favorably to the earlier work of Auger, Marciano, and Coulouvrat, but their new scheme is more efficient by a factor of four.
• Sambadam Baskar of University Pierre and Marie Curie present- ed a new nonlinear ray theory including the effects of shocks, diffraction, and atmospheric effects with co-author Phoolan Prasad. The current theory is only directly applicable to the for- ward part of an airfoil and work is ongoing to extend the theory for the trailing part of the airfoil.
• Ken Plotkin of Wyle Laboratories gave two papers at the meet- ing. One described his latest work with Ed Haering and Jim Murray of NASA Dryden Research Center analyzing the sonic boom data from sounding rockets having a peak overpressure of approximately 0.2 psf, much quieter than most sonic booms. They found that current models for oxygen and nitrogen relax- ation absorption in the atmosphere correctly describe the shock structure observed in their measurements. Plotkin's second paper was coauthored with Brenda Sullivan of NASA Langley Research Center and Domenic Maglieri of Eagle Engineering and described the measured effects of turbulence on and the perceived loudness of sonic booms from the SSBE experiments described earlier. Having developed a “de-turbing” process to remove the effects of turbulence from measured sonic booms, Plotkin was able to show that the root-mean-square values of the spiky fine structure near the jumps in a sonic boom agree well with the predictions of Steve Crow from 1969. The same data showed that the front-shock shaping of SSBE provided approxi- mately a 5 dB reduction in loudness using Steven's Mark VII perceived level.
• Michael Boudoin, along with co-authors Francois Coulouvrat and Jean-Louis Thomas, presented an initial study on the effects of clouds on sonic boom propagation. Using physically based
models, Boudoin showed that the absorptive effects of clouds are either comparable to or greater than traditional relaxation-based absorption mechanisms. To the present author's knowledge, this is the first time the effects of clouds have been explicitly consid- ered along with sonic boom propagation.
• Lance Locey presented a paper on developing appropriate filter functions that can add realistic features of atmospheric turbulence to synthesized sonic booms. This work is in conjunction with the present author and is funded by the FAA/NASA/Transport Canada PARTNER Center of Excellence, described earlier. The motivation for this research is to provide the effects of a realistic atmosphere to “clean” waveforms provided by industry before playback to subjective testing participants.
• Nicholas Heron from Dassault Aviation presented a paper along with several coauthors giving an overview of the low-boom design process currently in use at Dassault. A current design on the drawing board, for example, includes canards (winglets) on the forward part of the aircraft having a backward sweep and a down- ward twist. Their conclusion is that sonic boom minimization requires a substantial change in the shape of the aircraft.
• Sergei Chernyshev, representing several authors of the Central Aerohydrodynamics Institute (TgAGI) in Moscow, Russia, gave an overview of sonic boom research in that country. The effects of atmospheric turbulence on the propagation of sonic booms from TU-144 aircraft were noted, as well as the notion that the accurate prediction of both primary and secondary sonic boom is challenging for a realistic atmosphere. Aircraft modification including low-boom design simultaneous with high aerodynam- ic efficiency was also highlighted.
• Philippe Blanc-Benon of Ecole Centrale de Lyon described some of his recent work with his colleagues on describing the rise
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