Oct. 17, 2018
Discovery hailed as ‘new horizon’ in hypersonic flight
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Mohamed Gad-el-Hak, Ph.D., professor emeritus in the College of Engineering, together with investigators at Peking University in China, has revealed an aerodynamic heating mechanism that sheds new light on the behavior of ultra-high-speed aircraft. The discovery comes as China, the United States and Russia vie for dominance in hypersonic systems — aircraft and weapons that travel more than five times the speed of sound.
Researchers previously thought sudden heat spikes, which make hypersonic flight impractical for many applications, occur when air flows reach maximum turbulence. However, Gad-el-Hak and his collaborators have demonstrated that temperatures actually jump just before turbulence sets in. The National Science Review has called their achievement “a major progression in hypersonic transition.” The American Institute of Physics said the investigation denotes “a new horizon” for future studies of hypersonic heating phenomena.
For the past five years, Gad-el-Hak and his collaborators have studied the physics of turbulence to better understand the impact and behavior of air flow around objects that are accelerating in space. When air — or fluid — flows slowly, the flow is smooth. As the flow gets faster, it becomes more turbulent. This complex process, called the laminar-to-turbulence transition, is not fully understood. A better understanding of that transition is essential to the realization of hypersonic travel.
Technology for hypersonic flight exists but is expensive and risky largely because of the heat caused by transitioning from smooth to turbulent flows. The team has pinpointed the unstable phase between smooth flow and turbulent flow — called the second mode of instability — as the precise moment when temperatures peak.
This new understanding has applications in the design of future spacecraft, intercontinental ballistic missiles and hypersonic vehicles — as well as future inventions. The discovery was made through Gad-el-Hak’s efforts in fundamental research, which seeks to improve scientific understanding of the natural world.
“A distinguishing characteristic of basic research is its occasional spark to new frontiers unimagined in applied research,” Gad-el-Hak said, adding that global positioning systems, satellite radio and “a mathematical problem that metamorphosed into Google” are just a few examples of game-changing innovations that grew out of fundamental research.
Given sufficient latitude, “humans tend to discover what is not yet discoverable,” he said. “Organized, long-term basic research pays dividends you don’t see from the more random, shorter-sighted research model that is prevalent today. This point applies to everything from fighting diseases to fulfilling our energy need. It is much bigger than hypersonic flights or weapons.”
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