Dr. Earl H. Dowell
ABSTRACT
Hypersonic flight is a major challenge and substantial
efforts are currently underway to provide the understanding and technology
required to design and operate effectively and safely a hypersonic aircraft for
commercial or military purposes. Ivett Leyva [1] has recently described the
essence of this challenge in an article in Physics Today, November 2017.
There are several key physical phenomena that can occur in
hypersonic flight that involve fluid/structural/thermal/dynamics interaction
(FSTDI). This talk is an effort to bring some order to this complex
multidisciplinary topic. Issues
involving only two disciplines are identified that need further work as well as
issues that are relatively well understood. Then the discussion moves to issues
involving three disciplines (FSDI) and finally to FSTDI in its full four
discipline form.
To bring some order to the complexity the focus of the talk
will be on (1) response of structures to known turbulent flows, (2) global
dynamic instability of the flow field due to shock wave/ boundary layer
interaction, (3) dynamic instability of
the combined fluid structural system (flutter and limit cycle oscillations),
and (4) effects of thermal fields on the foregoing and vice versa.
The number of non-dimensional parameters that can affect
these physical phenomena is large. These non-dimensional parameters include the
following: Mach Number, Reynolds Number, the ratio of flow dynamic pressure to
structural stiffness, the ratio of fluid mass to structural mass, the ratio of
static pressure loading to structural stiffness, and the ratio of thermal
stress induced by a temperature difference between the flexible structure and
its surrounding structure to flexible structure stiffness as well as the
geometry (e.g. length to width ratio) of the structure. When multiple
disciplines are involved the number of relevant non-dimensional parameters is
indeed daunting. Thus theory and computation are very much needed as a valuable
guide to the design and interpretation of experiments.
BIOGRAPHY
Dr. Dowell is an elected member of the National Academy of
Engineering, an Honorary Fellow of the American Institute of Aeronautics and
Astronautics (AIAA) and a Fellow of the American Academy of Mechanics and the
American Society of Mechanical Engineers. He has also served as Vice President
for Publications and member of the Executive Committee of the Board of
Directors of the AIAA; as a member of the United States Air Force Scientific
Advisory Board; the Air Force Studies Board, the Aerospace Science and
Engineering Board and the Board on Army Science and Technology of the National
Academies; the AGARD (NATO) advisory panel for aerospace engineering, as
Presi-dent of the American Academy of Mechanics, as Chair of the US National
Committee on Theoretical and Applied Mechanics and as Chair-man of the National
Council of Deans of Engineering. From the AIAA he has received the Structure,
Structural Dynamics and Materials Award, the Von Karman Lectureship the
Crichlow Trust Prize and the Reed Aeronautics Award; from the ASME he has
received the Spirit of St. Louis Medal, the Den Hartog Award and Lyapunov
Medal; and he has also received the Guggenheim Medal which is awarded jointly
by the AIAA, ASME, AHS and SAE. He has served on the boards of visitors of
several universities and is a consultant to government, industry and
universities in science and technology policy and engineering education as well
as on the topics of his research. Dr. Dowell research ranges over the topics of
aeroelasticity, nonsteady aerodynamics, nonlinear dynamics and structures. In
addition to being author of over three hundred research articles, Dr. Dowell is
the author or co-author of four books, "Aeroelasticity of Plates and
Shells", "A Modern Course in Aeroelasticity", "Studies in
Nonlinear Aeroelasticity" and “Dynamics of Very High Dimensional Systems”.
His teaching spans the disci-plines of acoustics, aerodynamics, dynamics and
structures. Dr. Dowell received his B.S. degree from the University of Illinois
and his S.M. and Sc.D. degrees from the Massachusetts Institute of Technology.
Before coming to Duke as Dean of the School of Engineering, serving from
1983-1999, he taught at M.I.T. and Princeton. He has also worked with the
Boeing Company.