J. Gordon Leishman

United States of America

 

  1. Gordon Leishman, Distinguished Professor of Aerospace Engineering

Embry-Riddle Aeronautical University

Professor J. Gordon Leishman leads the effort now building a state-of-the-art wind tunnel laboratory at Embry-Riddle Aeronautical University (ERAU) in Daytona Beach, Florida. He came to the renowned aviation and aerospace school in 2014 following a distinguished research and teaching career at the University of Maryland. “I officially retired on a Friday and started working at ERAU the following Monday. Embry-Riddle asked me if I would help establish their Ph.D. program and help move the Aerospace Engineering Department more into the research arena.” Central to ERAU’s new research focus is an advanced subsonic wind tunnel scheduled to open for academic and industry research, as well as for teaching by the end of 2017. “There’s a lot of aerospace industry in Florida, Georgia, [and] Texas, and we felt having a state-of-the-art wind tunnel research facility at ERAU would be good for the industry too.”

Leishman continues to teach undergraduate aerodynamics and graduate-level helicopter aerodynamics at ERAU. “The university takes teaching very seriously,” he observed. The engineering school has about 1,300 undergraduate aerospace engineering students and will graduate its first three doctoral students this December. “There are some very excellent students here. In my first year at ERAU, I taught my helicopter class just the same as I taught it at Maryland and had 19 students get 19 A’s — very high-caliber students. We expect to keep a few of these students in the Ph.D. program.” Leishman’s previous doctoral students have gone on to take positions at DARPA, Sikorsky Aircraft, Boeing, Leonardo Helicopters, Airbus and other government and industry rotorcraft centers.

The distinguished researcher has been a private pilot for more than 40 years and continues to fly his Piper Cherokee. “Flying and engineering go hand in hand as far as I’m concerned. The flying is the application part,” he offered. “That’s one of the reasons I like Embry-Riddle — there’s a very strong synergy between the engineering and the flying.”

Growing-Up Global
Leishman spent his early years in Falkirk on the Scottish Lowlands between Edinburgh and Glasgow. His father, John, was a marine engineer for Mobil Oil Corp. “I was always involved with ships when I was growing up, and I used to spend a lot of time following my dad around doing engineering stuff — it’s kind of in my blood, I guess.” Oil industry assignments took the Leishman family to Baltimore, Maryland, in the US; and then to Japan, where Gordon attended a US Navy school. “I grew up in both the British culture and American culture.”

Subsequent transfers sent the Leishmans to New York City and then back to Scotland. When his parents went on to Scandinavia, Leishman pursued pre-university studies at Strathallan, a prestigious private school in the UK. “That was really where I discovered my interest in math and science,” he recalled. “It really helped me realize I wanted to become an engineer. I discovered there I had a flair for math and experimentation — I was always very interested in physics and to some degree chemistry... I was always interested in airplanes too. I was more interested in engineering rather than flying as a career, but I was always interested in aviation.”

The University of Glasgow, about 50 m (80 km) from Falkirk, had a powerful draw. “Glasgow had a rich history in engineering — the first professor of engineering at Glasgow was William Rankine. They had a very strong aerospace department — at that time it was the aeronautical engineering department.” Leishman majored in aeronautics and fluid mechanics and graduated with first-class honors in 1980. “I don’t think then any aeronautical engineering department taught much if anything about helicopters. I remember learning about propeller theory, but nothing about helicopters.”

A senior-year advisor nevertheless told the young engineer of a grant research project sponsored by Westland Helicopters 500 m (800 km) south in Yeovil, England. “Westland at that time was pursuing, fairly aggressively, advanced rotor designs to increase forward speed, primarily of the Lynx helicopters,” explained Leishman. “One of the barriers to higher forward speeds was retreating blade stall, so they were very interested in better understanding the physics of the problem and developing better mathematical models for use in their rotor design studies. As part of my Ph.D. research, I was given the problem of setting up an experimental facility in the large wind tunnel at Glasgow University to study dynamic stall.”

Westland hired the graduate researcher as an aerodynamicist in 1983 and gave him time to finish his Ph.D. dissertation. Collaboration with fellow aerodynamicist Tom Beddoes led to the Leishman-Beddoes dynamic stall model widely used today. The work also advanced the British Experimental Rotor Program (BERP) that took the Westland Lynx to helicopter record speeds. Leishman recalled, “The state of computer technology at that time was rather limited. There was a lot of emphasis on computational brevity. There was no such thing as computational fluid dynamics [CFD]; that only came about towards the end of the 1980s.” He added, “Westland invested an enormous amount of time validating their computational methods. It gave me a very good grounding in what these comprehensive codes did in terms of aerodynamics, structural dynamics, aeroelasticity, performance, loads, the whole gamut.”

The Leishman-Beddoes paper presented at the AHS Forum in Washington in May of 1986 also led to lasting professional connections. “I had the opportunity to meet a lot of new people in the helicopter community, including Professor [Inderjit] Chopra from the University of Maryland. He asked me if I’d be interested in coming to Maryland to work as a post-doc. Westland had been going through an awkward phase of uncertainty, and I said, ‘yes, let me do that.’”

The Maryland Years
The new Maryland post coincided with the early days of the Rotorcraft Center of Excellence. “I worked with many Ph.D. students there, teaching them about unsteady aerodynamics, aerodynamic stall, integrating the Leishman-Beddoes model into their rotor analyses,” said Leishman. “I also began diversifying into other areas, one of which was rotor-airframe interactions.”

A faculty opening in 1988 made Leishman an assistant professor in the Aerospace Engineering department and saw him steering a range of scientific investigations. “What stands out as I look back was the very highly interdisciplinary advancements that were made during that time,” he noted. “The significant advancements … included the synergistic aspects of bringing the different traditionally separate disciplines together and beginning to really understand the fundamental problems limiting helicopters and other rotorcraft.”

In 2007, an Air Force-funded Multi-disciplinary University Research Initiative (MURI) addressed the blinding brownout created by helicopters in dust. Leishman explained, “The goal of the MURI was to understand the fluid mechanics of the problem. What are the parameters that govern the intensity of the dust cloud? If we understood that, perhaps we could begin to think about how to reduce the severity of the brownout problem…. There’s a very complicated coupling between the air flow produced by the rotor and the behavior of the dust.”

He added, “We set to work looking at brownout from a fundamental fluid mechanics perspective, both from measurement and modeling.” Student researchers developed computer codes and studied both obscurants and the “vection” illusion of movement caused by a moving dust cloud. Leishman observed, “One of the big challenges at a university is taking the fundamental science to the next level. One of my Ph.D. students, Monica Syal, spent a lot of time looking at the modeling of rotor wakes and brownout simulations. She went to work for ART — Advanced Rotorcraft Technologies — to take her research to the next level and bring that modeling of the visual aspects of the cloud.” The work transitioned the fundamental science to training simulators. [Syal is now at Airbus.]

Life in Florida
With the MURI coming to an end, Leishman and his wife looked to retire from the University of Maryland. “We wanted to move to Florida, and in 2013, I heard that Embry-Riddle was thinking of building a new wind tunnel facility. I was very excited about continuing to do professor-type work, teaching, and getting involved with a university that also had a very embryonic graduate program.”

The ERAU wind tunnel was designed with the aid of CFD and built by FluiDyne. It has a 6 ft by 4 ft (1.8 m by 1.2 m) cross-section stretching through a 12 ft (3.7 m) long standard test section and a 20 ft (6.1 m) alternative section. The large fan is driven by a 1,200 hp (900 kW) motor. “We have the ability to reach about 250 mph [400 km/h] in the test section,” explained Leishman. “A lot of the tunnels in this class are in the 160- to-200 mph [260- to 320-km/h] range.” The tunnel test section is also notable for its many windows. “To do particle image velocimetry [PIV] in the wind tunnel is very challenging, in part because of the need for good optical access,” observed Leishman. “You have to create a very thin laser sheet and image the sheet with multiple cameras, so you have to have lots of windows.”

Leishman also advises ERAU researchers at the Eagle Flight Research Center working to overcome the limitations of traditional rotorcraft. “In the last 20 years, there have been a lot of advancements in understanding these problems, particularly because we can do much better experiments, and we also have the help of CFD. Then comes the challenge of putting these ideas into practice, such as ways of alleviating retreating blade stall. You may be able to demonstrate methods of mitigation in a laboratory, but the challenge comes when putting them on a helicopter compounded by weight, complexity, failure modes, and certification issues. Embry-Riddle is very strong on design engineering but also very strong on the actual practice of putting the engineering on an aircraft.”

Rotorcraft have made significant advances in recent years. Leishman observed, “We’ve seen the X2 program. We’ve seen the DARPA VTOL X-Plane program led by one of my former Ph.D. students, Ashish Bagai, trying to drive the industry to more innovative solutions that make helicopters and rotorcraft do more. That’s very exciting for me to see. Thinking a little out of the box opens opportunities to do more. The key is being able to morph the vehicle from being a helicopter limited by an edge-wise operating rotor to fly like an airplane. A tiltrotor is a good example of that, but it isn’t necessarily a very good compromise. That’s why some of these distributed electric propulsion concepts are so interesting — not so much the distributed propulsion per se but the ability to morph from a helicopter to being more of an airplane.”

Since he joined AHS in 1986, Leishman and his graduate research students have presented more than 60 papers. “AHS is a small community, a very tight-knit community,” he concluded. “The AHS Forum has always been the highlight of my professional year — to present our work, to get the feedback from our peers, our academic colleagues, our industry partners, and help focus the research for the following year.”

Vertiflite Leadership Profile: Vertiflite January/February 2017