Going with the flow
Researching air flow dynamics is not everyone's idea of a summer vacation, but Kettering graduate student Richard Anderson thought it was great.
Plasma interaction with aerodynamics is one of the hot new areas of research to improve flow control technology in gas turbine engines - like those used in aircraft. Kettering University has four researchers working on improving flow control using glow-discharge plasma.
Richard Anderson, a graduate student in Mechanical Engineering, and Dr. Subrata Roy, associate professor of Mechanical Engineering, are collaborating with Dr. K.P. Singh, post doctoral research assistant in Research, Haribalan Kumar graduate student in Mechanical Engineering, on research to perform computer modeling and physical testing of air flow dynamics for the Air Force Research Laboratory in Dayton, Ohio. The project is sponsored by the Air Force Office for Scientific Research.
Anderson, who has an undergraduate degree in Aerospace Engineering, spent two months at the Dayton lab doing computer simulations of what they expect to see in the wind tunnels when physical testing begins in Kettering's Computational Plasma Dynamics Laboratory this fall. "We'll be doing physical research to validate our computer modeling," said Anderson, of St. Joseph, Mich.
He was happy to spend his summer in front of the computer. "The fellowship allowed me to work for the Air Force during the summer, which is unique because most graduate students only have one graduate research project, this 'extra curricular' research is real world research," Anderson said.
"Kettering is one of the few universities doing research in the area of plasma dynamics and plasma interactions with aerodynamics, or what we call 'flow control'," said Anderson.
"Flow control" means a technology by which a very small input results in a very large effect on the flow, according to an article on the topic written by Dr. David E. Ashpis and Dr. Lennart S. Hultgren for NASA's Glenn Research Center web site. A number of flow control devices, including glow-discharge plasma devices, have been shown to impact the external aerodynamics of aircraft wings and airframes.
"What has been found," said Anderson, "is that if you take two electrodes and separate them with Kapton, a silicon plastic film, and then run an electrical current through them at approximately 2,000 volts, the air around them will become ionized. And, if you are pushing air flow past this device you will get more speed near the wall of the turbine than normally expected," he said.
What this translates to is the ability to achieve more lift on aircraft wings at a greater angle before stall occurs. "When a wing is tipped back the air comes off the top of the wing and you lose lift," said Anderson, "it stalls." Early research using glow-discharge plasma devices shows an increase in the degree of the angle before stall occurs. "Before, wings began to lose lift at 15-20 degrees of incline," Anderson said, "with this device it stalls at 20-25 degrees.
"Our research is building on that done by Dr. Thomas Corke of Notre Dame, whose research has shown this device to work at speeds well below Mach 1," Anderson said. "Dr. Roy is hoping to increase the speed used by Corke, and the Air Force would like us to demonstrate at much higher speeds. When we test it in a wind tunnel we are hoping it will demonstrate at Mach .5 or hopefully even Mach 1," said Anderson.
The Air Force is looking at the technology as a way to redesign aircraft. For example: if a design called for the removal of the wing flaps, they could be replaced with the glow-discharge plasma device for a smooth wing, resulting in a reduction of drag on the wing.
The Research Institute for Autonomous Precision Guided Systems at the University of Florida Graduate Engineering and Research Center (GERC) web site states that "aerodynamic flow control by means of plasma actuator devices have experimentally shown their ability to reattach separated flow at high angles of attack, as well as an ability to induce flow movement in an initially stationary air mass. The use of plasma actuators in such a role may offer several advantages over traditional flow control devices (eg: slats, flaps, slots). Some of these advantages may be reduced size and weight, no moving parts (leading to improved manufacturability), increased reliability, reduced drag, high bandwidth (quick response), increased aerodynamic agility, low cost and no tail fins (leading to increased weapon load-out of combat A/C)."
The next step for Anderson and Roy is to actually construct their flow control device and test it in a wind tunnel. They expect to have results for this next step in time for the conference of the American Institute of Aeronautics and Astronautics (AIAA) in January 2006.
Written by Dawn Hibbard