Title page for ETD etd-91498-143821

Type of Document

Dissertation

Author

Preidikman, Sergio

Author's Email Address

spreidik@vt.edu

URN

etd-91498-143821

Title

Numerical Simulations of Interactions Among Aerodynamics, Structural Dynamics, and Control Systems

Degree

PhD

Department

Engineering Mechanics

Advisory Committee

Advisor Name	Title
Mook, Dean T.	Committee Chair
Batra, Romesh C.	Committee Member
Durham, Wayne C.	Committee Member
Hendricks, Scott L.	Committee Member
Nayfeh, Ali H.	Committee Member
Perumpral, John V.	Committee Member
Wolfe, Mary Leigh	Committee Member

Keywords

Flutter
Unsteady Nonlinear Aeroelasticity
Wings

Date of Defense

1998-10-01

Availability

unrestricted

Abstract

A robust technique for performing numerical simulations of nonlinear
unsteady aeroelastic behavior is developed. The technique is applied to
long-span bridges and the wing of a modern business jet. The heart of the
procedure is combining the aerodynamic and structural models. The
aerodynamic model is a general unsteady vortex-lattice method. The
structural model for the bridges is a rigid roadbed supported by linear and
torsional springs. For the aircraft wing, the structural model is a
cantilever beam with rigid masses attached at various positions along the
span; it was generated with the NASTRAN program. The structure, flowing air,
and control devices are considered to be the elements of a single dynamic
system. All the governing equations are integrated simultaneously and
interactively in the time domain; a predictor-corrector method was adapted
to perform this integration.
For long-span bridges, the simulation predicts the onset of flutter
accurately, and the numerical results strongly suggest that an actively
controlled wing attached below the roadbed can easily suppress the
wind-excited oscillations. The governing equations for a proposed passive
system were developed.
The wing structure is modelled with finite elements. The deflections are
expressed as an expansion in terms of the free-vibration modes. The
time-dependent coefficients are the generalized coordinates of the entire
dynamic system. The concept of virtual work was extended to develop a method
to transfer the aerodynamic loads to the structural nodes. Depending on the
speed of the aircraft, the numerical results show damped responses to
initial disturbances (although there are no viscous terms in either the
aerodynamic or structural model), merging of modal frequencies, the
development of limit-cycle oscillations, and the occurrence of a
supercritical Hopf bifurcation leading to motion on a torus.

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	bibliography.pdf	89.55 Kb	00:00:24	00:00:12	00:00:11	00:00:05	< 00:00:01
	chapter1.pdf	461.57 Kb	00:02:08	00:01:05	00:00:57	00:00:28	00:00:02
	chapter2.pdf	2.42 Mb	00:11:12	00:05:45	00:05:02	00:02:31	00:00:12
	chapter3.pdf	1.14 Mb	00:05:17	00:02:43	00:02:22	00:01:11	00:00:06
	chapter4.pdf	297.37 Kb	00:01:22	00:00:42	00:00:37	00:00:18	00:00:01
	chapter5.pdf	7.16 Mb	00:33:08	00:17:02	00:14:55	00:07:27	00:00:38
	chapter6.pdf	35.79 Kb	00:00:09	00:00:05	00:00:04	00:00:02	< 00:00:01
	introduction.pdf	95.11 Kb	00:00:26	00:00:13	00:00:11	00:00:05	< 00:00:01