1. AAE 556 Aeroelasticity Lectures 10 and 11
Swept wing aeroelasticity
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2. Mid-term exam March 9, evening 1.5 hours
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3. Swept wing static aeroelasticity Reading Sections 3.1 through 3.4
Goals
Determine how bending changes aeroelastic loads on swept wings
review simple aerodynamic model and simple stiffness model
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The letter N
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5. Lift on flexible wing model
Use the airspeed component normal to the wing to define dynamic pressure
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6. Objective -wing structure idealization with aerodynamic loads
springs resist upward and downward motion
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7. Wing aerodynamic forces matching downwash for lift computation
Streamwise coordinates are the favorite of aero people, but I’m a structures guy
What is “downwash?”
freestream view
chordwise view v v
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8. “Preserving” downwash velocity – angle of attack equivalence
What angle of attack, when multiplied by YOUR definition of dynamic pressure gives the correct airloads?
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9. Lift on flexible wing model
Use the airspeed and dynamic pressure components normal to the wing
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10. Equations of bending and torsional static equilibrium
“Bending” equilibrium about the x-axis (f)
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11. Twisting moment equilibrium about y-axis (q)
static torsional equilibrium
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12. Define (encrypt) problem parameters
static equilibrium equations with initial angle of attack or
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13. Combine matrices - final resultor
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14. Determinant (D) of aeroelastic stiffness matrix
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Divergence condition
so that
Hmmm - only one divergence q for a 2 DOF system?
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16. Eliminate divergence? Just sweep the wing
Set denominator equal to zero
No divergence if
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example
Torsional stiffening is still good
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example
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19. Purdue Aeroelasticity
Summary
Bending deflection creates lift reduction
Divergence does not occur if the sweep angle is more than about 5 degrees
Lift effectiveness is reduced
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