The Duke University Wind Tunnel is a subsonic wind tunnel that is located in the basement of the Hudson building annex. The wind tunnel is a large experimental apparatus that is used frequently for aerospace engineering research as well as undergraduate class projects. The wind tunnel itself is approximately 20 feet tall, and has a footprint of 40 feet by 10 feet. The test section of the wind tunnel, in which experimental models can be placed, is about 50 inches long and has a cross section of 20 inches by 28 inches. The air flow through the test section is driven by a 75 hp electric motor, and can reach air speeds up to 60 m/s.
Duke’s wind tunnel is used extensively by the Duke Aeroelasticity Research Group, headed by Dr. Earl Dowell, and includes Professors Kenneth Hall, Laurens Howle, Robert Kielb and Lawrence Virgin. Currently active research projects include aeroelastic response of morphing wing aircraft, determining flutter boundaries for flexible membranes with various boundary conditions, unsteady aerodynamic and buffet studies of airfoils at very high angles of attack, and experimental demonstration of limit cycle oscillation behavior for an airfoil supported by springs with a novel geometrically nonlinear design. Previous projects include flutter and limit cycle oscillations of airfoils, control surfaces and wings with freeplay. Also gust response of all the above configurations has been studied and a gust response excitation system is available.
The Duke wind tunnel has a variety of data acquisition equipment. The air speed is measured by both a pitot static tube and a hot wire anemometer, calibrated specifically for the range of air speed for this particular wind tunnel. The signals from the two instruments are collected by a National Instruments DAQ system, and read by LabVIEW software on the wind tunnel’s dedicated computer. In addition, the DAQ system has one 8-channel current input module, three 8-channel voltage input modules, and one 8-channel voltage output module. Instruments for measuring experimental model motion include teardrop accelerometers, a laser velocity meter, pressure sensors and strain gauges. There is also a stand-alone spectrum analyzer that can acquire data and compute the frequency content and transfer function using on-board software.
Undergraduate students also use the wind tunnel for labs and design projects. Specifically, the undergraduate fluid mechanics course (ME126) uses the wind tunnel for a lab that demonstrates the concepts of lift and drag coefficient, and the senior design course (ME160) uses the wind tunnel for various senior design projects. Past projects include ram jet turbine design for aircraft emergency power units, testing a scaled model of a water turbine in the wind tunnel, and carbon fiber trailing edge flap system for high efficiency “green” aircraft.