AAE 55600: Aeroelasticity


Aeroelasticity is concerned with the consequences and trade-offs created by interactions between aerodynamic forces and structural deformation. Static aeroelastic problems; control effectiveness; lift effectiveness; divergence. Dynamic aeroelasticity; flutter and vibration.

Format: 3 hrs lecture per week

Credit hours: 3

Status: Elective, Structures

Offered: Spring

Pre-requisite: AAE 340 or equivalent

Co-requisite: None

Course Instructor: Prof. Weisshaar

URL: http://roger.ecn.purdue.edu/~aae556/

Text: Aircraft Aeroelastic Analysis and Design, Terrence A. Weisshaar, 1995

Assessment Method: Midterm exam 30%, Final exam 30%, Homework, projects 40%


Course Objective: Prediction of aero/structural interactions and the ability to model, analyze and control aircraft aeroelastic phenomena, including aerodynamic and control effectiveness aero-structural stability, both static and dynamic. Understanding the phenomenology of aero/structural interaction, not with complicated modeling processes themselves.


Objectives include developing abilities to:

Model aeroelastic aero-structure interactions that create phenomena such as divergence, lift effectiveness and control effectiveness

Predict structural instabilities such as flutter and divergence

Calculate unsteady aerodynamic forces for elementary wings

Necessary Background: The material is relatively self-contained in that we will introduce concepts such as mass and stiffness matrices, shear centers, aerodynamic coefficients and aerodynamic centers and then build on these concepts

1. Ability to model and analyze discrete, vibrating mechanical systems.

2. Knowledge of basic structural principles.

Topics (number of Lectures):

1. Introduction: goals, grading, expectations

2. Review and introduction of basis concepts: twisting of unswept wings, shear center, aerodynamics, aero/structural interaction, the typical section model (2 lectures)

3. Effects of aeroelastic flexibility, Stiffness changes and deflection effects on free flight of aircraft

4. Divergence and static stability, airfoil twist angle amplification, aeroelastic feedback (2 lectures)

5. Stability solution approach, example, nonlinearity, examples (2 lectures)

6. Effects of compressibility on wing divergence

7. Multi-degree-of-freedom systems, strip theory aerodynamics, aeroelastic stiffness matrix (3 lectures)

8. Divergence of continuous wing model (2 lectures)

9. Aileron reversal (2 lectures)

10. Active control for static aeroelastic problems - an example of how loads are fed back to stabilize a wing (2 lectures)

11. Swept wing aeroelasticity, semi-rigid model, matrix equations, lift on flexible wing, divergence (3 lectures)

12. Swept wing lift effectiveness. (2 lectures)

13. Flexural axis and aeroelastic tailoring (2 lectures)

14. Midterm Review

15. Dynamics and vibration of typical section. Vibration of typical section with torsion - finding divergence from a dynamics perspective (2 lectures)

16. Equations of free vibration in matrix form, eigenvalues & mode shapes, node lines and points (3 lectures)

17. Quasi-steady aerodynamic modeling, airfoil free vibration model

18. Representation of free vibration with complex numbers, stability and flutter (2 lectures)

19. Unsteady aerodynamics, representation of relationship between forces and motion, lags. state space models (6 lectures)

20. Forced harmonic motion with unsteady aerodynamics (2 lectures)

Relationship of course to program objectives:

This is an elective course that emphasizes the need for integration between aerodynamics and structures and the new phenomena that can arise from this interaction. (1). The ability to formulate and solve engineering problems (2a) is emphasized in the lectures, homework assignments and small projects. Aeroelastic effects have resulted in major accidents and historically significant events. Professional conduct (2d) and societal impact (4) are discussed throughout the course

Prepared by: T. A. Weisshaar

Date: 25 February 2001