
Earl H. Dowell, William Holland Hall Professor of Mechanical Engineering in the Edmund T. Pratt, Jr. School of Engineering and CNCS: Center for nonlinear and complex systems and Faculty Network Member of The Energy Initiative and Affiliate of the Duke Initiative for Science & Society
Professor Dowell's principal teaching interest and research activity is in the field of aeroelasticity  which is the study of the dynamic interaction between an aerodynamic flow and an elastic structure, such as aircraft wings in high speed flight, long span bridges and tall buildings responding to wind loadings, or airflow through the mouth and lungs. Dr. Dowell has also done research in acoustics, nonlinear dynamics, structural dynamics, and unsteady aerodynamics.
Professor Dowell's major research accomplishments include the first definitive research monograph on the aeroelasticity of plates and shells, the first derivation and solution of the nonlinear equations of motion for a helicopter rotor blade (the HodgesDowell equations), and work with Professor Kenneth Hall and several graduate students and postdoctoral fellows on reducing the dimensions of mathematical models for very complex highdimensional fluid/structural systems. Professor Dowell teaches undergraduate and graduate courses on dynamics and aeroelasticity.
Here are seven short videos showing experimental aeroelastic models undergoing limit cycle oscillations in the Duke wind tunnel.
 An airfoil with a nonlinear freeplay in the connection from the main airfoil to the trailing edge control surface.
 A delta wing with a strong structural nonlinearity as a result of tension in the midplane of the platelike wing induced by bending of the wing out of its initially undeformed plane.
 A very high aspect ratio wing that behaves as a beam with double bending (both transverse to and inline with the aerodynamic flow field) and twisting. A nonlinear coupling among double bending and twisting occurs. Also the aerodynamic flow field experiences separation due to the large motions involved.
 A delta wing with an external store, flutter and limit cycle oscillations.
 LCO and Flutter of WingStore model
 Flapping Flag Flutter
 LCO of Cropped Delta Wing In the video you will see a cropped delta wing (that simply means we cropped off that would otherwise be a delta or triangular wing). The wind speed in the wind tunnel is shown by the dial in one of the frames. In the other two frames you see signals from two strain gauge bridges, bending and torsion, and of course the wing itself.
The wind speed at which flutter is predicted to occur theoretically is about 19 meters/second. The experimental flutter speed based on observation of the strain gauge signals is about 21 meters/second. Note that at the wind speed when flutter starts, both strain gauges show dominant response at a frequency of 12 Hz. This large peak at a single frequency is a characteristic identifier of flutter. Also note that the motion of the wing is not easily visible to the eye until a higher wind speed in the range of 2426 meters/second and the motion is most visible at the wing tip. Once the flutter speed is exceeded, limit cycle oscillations occur due a strong structural nonlinearity.
 Experimental Aeroelastic Models: Design and Wind Tunnel Testing for Correlation with New Theory  An overview of Wind Tunnel Testing in Duke University
 Contact Info:
 Education:
MS  Massachusetts Institute of Technology (MIT)  1964 
PhD  Massachusetts Institute of Technology (MIT)  1964 
D.Sc.  Massachusetts Institute of Technology  1964 
M.S.  Massachusetts Institute of Technology  1961 
B.S.  University of Illinois  1959 
 Specialties:

Technology Transfer
Aerodynamics Chaos, Dynamics Policy, Science and Engineering Acoustics Aerospace Aeroelasticity Nonlinear Systems
 Research Interests:
Broad field of aeroelasticity, acoustics, nonlinear dynamics, structural dynamics, and unsteady aerodynamics.
 Keywords:
Acoustics • Aerodynamics • Architectural acoustics • Art • Composite materials • Computational fluid dynamics • Computer Simulation • Differential equations • Elastic waves • Elasticity • Finite Element Analysis • Flow visualization • Interpolation • Kinematics • Laminar flow • Library Automation • Mathematical models • Models, Theoretical • Motion • Oscillations • Particle image velocimetry • Pressure • Shear flow • Special libraries • Time Factors • Turbulence
 Recent Publications
(More Publications)
 Ding, H; Dowell, EH; Chen, LQ, Transmissibility of Bending Vibration of an Elastic Beam,
Journal of Vibration and Acoustics, vol. 140 no. 3
(June, 2018) [doi] [abs]
 Culver, D; Dowell, E, Iterative techniques for analyzing nonlinear vibrating dynamical systems in the frequency domain,
Nonlinear Dynamics, vol. 91 no. 4
(March, 2018),
pp. 21132140 [doi] [abs]
 Tang, D; Dowell, E, Aeroelastic response and energy harvesting from a cantilevered piezoelectric laminated plate,
Journal of Fluids and Structures, vol. 76
(January, 2018),
pp. 1436 [doi]
 Ding, H; Tan, X; Dowell, EH, Natural frequencies of a supercritical transporting Timoshenko beam,
European Journal of Mechanics  A/Solids, vol. 66
(November, 2017),
pp. 7993 [doi]
 Li, Z; Zhang, P; Pan, T; Li, Q; Zhang, J; Dowell, EH, CatastropheTheoryBased Modeling of AirfoilStall Boundary at Low Reynolds Numbers,
AIAA Journal
(October, 2017),
pp. 110 [doi]
