Earl H Dowell
William Holland Hall Professor of Mechanical Engineering in the Edmund T. Pratt, Jr. School of Engineering
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 Hodges-Dowell equations), and work with Professor Kenneth Hall and several graduate students and post-doctoral fellows on reducing the dimensions of mathematical models for very complex high-dimensional 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 mid-plane of the plate-like 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 in-line 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 24-26 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.
Appointments and Affiliations
- William Holland Hall Professor of Mechanical Engineering in the Edmund T. Pratt, Jr. School of Engineering
- Professor of Mechanical Engineering and Materials Science
- Affiliate of the Duke Initiative for Science & Society
- Faculty Network Member of The Energy Initiative
- Office Location: 185 Hudson Hall, Durham, NC 27708
- Office Phone: (919) 660-5302
- Email Address: firstname.lastname@example.org
- D.Sc. Massachusetts Institute of Technology, 1964
- M.S. Massachusetts Institute of Technology, 1961
- B.S. University of Illinois, 1959
Aeroelasticity, 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 conducted research in acoustics, nonlinear dynamics, structural dynamics, and unsteady aerodynamics.
Policy, Science and Engineering
Awards, Honors, and Distinctions
- Daniel Guggenheim Medal. American Institute of Aeronautics and Astronautics. 2009
- Den Hartog Medal. ASME. 2009
- Spirit of St. Louis Medal. American Society of Mechanical Engineers. 2008
- Walter J. and Angeline H. Crichlow Trust Prize. American Institute of Aeronautics and Astronautics. 2007
- Honorary Fellow. AIAA. 2004
- Theodore von Karman Lectureship Award. American Institute of Aeronautics and Astronautics. 2001
- Board of Governors. Research Triangle Institute. 1994
- Distinguished Service Award. American Academy of Mechanics. 1994
- Elected Member. National Academy of Engineering. 1993
- Fellow. American Society of Mechanical Engineers. 1993
- CEE 625: Intermediate Dynamics: Dynamics of Very High Dimensional Systems
- EGR 393: Research Projects in Engineering
- ME 392: Undergraduate Projects in Mechanical Engineering
- ME 492: Special Projects in Mechanical Engineering
- ME 541: Intermediate Dynamics: Dynamics of Very High Dimensional Systems
- ME 555: Advanced Topics in Mechanical Engineering
- ME 759: Special Readings in Mechanical Engineering
- ME 775: Aeroelasticity
In the News
- Dowell Receives Highest Individual Honor for Achievement in Aeronautics (Jun 16, 2016)
- AIAA congratulates Earl Dowell (Apr 21, 2016 | American Institute of Aeronautics and Astronautics newsletter )
- Earl Dowell: Celebrating 75 Years of Duke Engineering (Jan 14, 2015)
- Earl Dowell: Will arming pilots stop a terrorist attack? (Apr 21, 2014 | The Huffington Post )
- Dowell, E, Hamilton’s principle and Hamilton’s equations with holonomic and non-holonomic constraints, Nonlinear Dynamics, vol 88 no. 2 (2017), pp. 1093-1097 [10.1007/s11071-016-3297-9] [abs].
- Dowell, E, Modal damping in a finite element model (L), The Journal of the Acoustical Society of America, vol 140 no. 4 (2016), pp. 2288-2289 [10.1121/1.4964341] [abs].
- Culver, D; Dowell, E, High frequency analysis of a plate carrying a concentrated nonlinear spring–mass system, Journal of Sound and Vibration, vol 379 (2016), pp. 84-105 [10.1016/j.jsv.2016.05.048] [abs].
- Lin, H; Wang, S; Dowell, EH; Dong, J; Ma, C, Dynamic characteristics of double-helical planetary gear sets under time-varying mesh stiffness, Journal of Harbin Institute of Technology, vol 23 no. 4 (2016), pp. 44-51 [10.11916/j.issn.1005-9113.2016.04.007] [abs].
- Sayag, MR; Dowell, EH, Linear Versus Nonlinear Response of a Cantilevered Beam Under Harmonic Base Excitation: Theory and Experiment, Journal of Applied Mechanics, vol 83 no. 10 (2016), pp. 101002-101002 [10.1115/1.4034117] [abs].