A Career on Wings: Earl Dowellâ€™s Long Fascination with Flight
For Earl Dowell, aerodynamics and structural dynamics expert and dean emeritus of Duke’s Pratt School of Engineering, a fascination with flight began years before he ever got close to an airplane.
“When I was a small boy in Illinois, I remember seeing airplanes overhead and thinking: ‘It would be fun to be there,’” recalled Dowell, who is William Holland Hall professor of mechanical engineering and materials science (MEMS).
In those days, “growing up, no one I knew flew in airplanes.” Dowell said he might have climbed in “a cockpit or two,” but it was only after a couple years of college, where he majored in aerospace engineering, that he would finally take his first flight in a small plane with a licensed pilot friend.
Countless flights later, Professor Dowell, now a long-established engineer-researcher in the field of aerospace who has served as an adviser on aircraft design and performance to the Air Force and NASA, is this year’s winner of The American Institute of Aeronautics and Astronautics (AIAA) Walter J. and Angeline H. Crichlow Trust Prize, an award sometimes referred to as the “Nobel of Aerospace.”
"Dowell’s research endeavors have led to major contributions to the flight safety of fighter aircraft and have also had a major impact on the design of both military and civilian aircraft,” said AIAA President Roger Simpson of Dowell’s honor, which is presented every four years for excellence in aerospace materials, structural design, structural analysis or structural dynamics. “In addition, his influence on engineering education, both in the sense of developing a world-class program at Duke and mentoring countless students, will be long-lasting."
Dowell received his award, consisting of a medal, a certificate of citation and a $100,000 honorarium, on April 25 at a conference in Honolulu.
Perhaps Dowell’s early interest in airplanes was in his genes. One of his uncles, not much older than he, also had an interest in planes, later becoming a pilot in the Air Force, he noted.
But for Dowell, like so many budding engineers, an early talent for math and science led him to pursue his interest through engineering at the University of Illinois. When it came time for graduate school, he targeted two schools, the Massachusetts Institute of Technology and the California Institute of Technology, where the authors of two seminal textbooks were professors at the time.
“I chose MIT because they offered me the most money,” Dowell admits. Notably, both textbooks are still in print 50 years after their publication, he said.
It was at MIT that Dowell began his work on the mathematical modeling of “things that fly,” working under John Dugundji on aeroelasticity--the study of the dynamic interaction between aerodynamic flows and airplane wings or other elastic structures. (Dugundji will was honored at the AIAA meeting in Honolulu, where he gave the principal invited lecture for the conference.)
After graduate school and some time spent as a “real engineer” at Boeing, Dowell became a faculty member at Princeton University, where he turned his first 10 years of research into a now-classic book, Aeroelasticity of Plates and Shells, referring to the light-weight skins that cover aircraft, launch vehicles and missiles.
After 18 years at Princeton, Dowell “took a gamble,” leaving for Duke, which by comparison wasn’t as well known at the time.
“I never had second thoughts about that decision, because I was too busy,” Dowell said. He spent most of his energy as dean focusing on raising money and recruiting faculty.
“If you have enough money and talented, hard-working people, everything else will happen that needs to happen,” he said. “But you need the players and the funds to support them.”
Speeding Aircraft Design
Throughout, Dowell has kept up his research efforts, tracing the field from the “dawn of computer simulation and modeling” to its current level of sophistication. In the beginning, the computer models were reasonably sufficient to predict how well a plane would fly and under what conditions they might start fluttering dangerously--a phenomenon that can cause them to break apart in midair--but they “never told the whole story,” he said.
For instance, the models couldn’t accurately predict how planes would operate once they reached the speed of sound, when the most powerful aerodynamic forces occur, necessitating a strong, and sometimes risky, reliance on flight testing.
“Today, we can compute right through that regime,” he said. “Though far from perfect, we’re pretty good at it and getting better. The challenge now is that the math models are so elaborate and intensive, it can take months” for a computer to crunch through them.
Some of Dowell’s most recent advances in the field, which he has made in collaboration with MEMS chair Kenneth Hall, Jeff Thomas, Deman Tang and others, have found ways to pare down those complicated models and, in turn, speed up the process of designing aircraft and evaluating their performance.
Instead of thousands or even millions of equations describing the flow field around an airfoil or wing over many thousands of time steps, the methods Dowell’s team has developed take advantage of predictable patterns, calculating the same information in just a handful of time steps, with many fewer equations.
Meanwhile, Dowell, and the many graduate and undergraduate students he has mentored and continues to mentor, still work on modeling and experimental efforts aimed at future generations of flight. “There are now exciting changes in airplane design,” Dowell said.
For example, he added, people are working to develop more airplanes that would fly without a pilot. “Whole swarms of small, unpiloted planes could be put in dangerous places, like war or disaster zones for combat or surveillance purposes, or even inside of volcanoes,” he said. Someday, even “white knuckle” passengers will fly in planes without pilots, he predicts.
The future might also hold faster, hypersonic planes that would fly at speeds many times faster than the speed of sound, morphing planes that could dramatically change shape to accommodate different mission requirements, and easy-fliers reliable and cheap enough that average people might pilot themselves around, he said.
With all that incredible possibility ahead, Dowell still finds the same magic in airplanes that he appreciated as a child.
“Airplanes are a miracle,” he said, “if you think about it.”
Dowell is the principal author of the leading textbook in aeroelasticity, A Modern Course in Aeroelasticity, now in its fourth edition. He is also a co-author of the now classic Aeroelasticity of Plates and Shells and of the most recent Dynamics of Very High Dimensional Systems. Additionally, he is the author or co-author of over 250 technical papers.
Dowell's honors include AIAA Honorary Fellow, Fellow of the American Society of Mechanical Engineers, Fellow of the American Academy of Mechanics, elected member of the National Academy of Engineering, past president of the American Academy of Mechanics, current service on the National Research Council, and others. His accomplishments have been recognized with the AIAA Theodore von KÃ¡rmÃ¡n Lectureship in Astronautics, AIAA Structures, Structural Dynamics and Materials Award, and the American Academy of Mechanics Distinguished Service Award in addition to the Crichlow Prize.