1. AAE 556 Aeroelasticity Lecture 10
Swept wing aeroelasticity
Part 1
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

2. Swept wing static aeroelasticity
Reading – pp
Goals
Determine how bending changes aeroelastic loads on swept wings
review simple aerodynamic model and simple stiffness model
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

3. Planform view of wing structure idealization model features
Why does bending create lift force????
The letter N
springs resist upward and downward motion
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

4. Lift on flexible wing model
Use the airspeed component normal to the wing to define dynamic pressure
HOW?
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

5. Wing aerodynamic forces matching downwash for lift computation
I know that the streamwise coordinates are the favorite of aero people, but I’m a structures guy
What is “downwash?”
freestream view
chordwise view v
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

6. “Preserving” downwash velocity – angle of attack equivalence
What angle of attack, when multiplied by YOUR definition of dynamic pressure gives the correct airloads?
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

7. Lift on flexible wing model
Use the airspeed component normal to the wing
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

8. Equations of bending and torsional static equilibrium
“Bending” equilibrium about the x-axis (f)
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

9. Twisting moment equilibrium about y-axis (q)
static torsional equilibrium
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

10. Define (encrypt) problem parameters
static equilibrium equations with initial angle of attack or
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

11. Combine matrices - final resultor
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

12. Determinant (D) of aeroelastic stiffness matrix
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

13. Copyright Purdue University 2008
Divergence condition
so that
Hmmm - only one divergence q for a 2 DOF system?
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

14. Eliminate divergence? Just sweep the wing
Set denominator equal to zero
No divergence if
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

15. Copyright Purdue University 2008
example
Torsional stiffening is still good
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

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example
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring

17. Copyright Purdue University 2008
Summary
Bending deflection creates lift reduction
Divergence does not occur if the sweep angle is more than about 5 degrees
Lift effectiveness is reduced
5/2/2019
Copyright Purdue University 2008
AAE556 – Spring