Aeroelasticity

Aeroelasticity basic concepts

1. SIDDARTHA INSTITUTE OF SCIENCE AND TECHNOLOGY PowerPoint presentation on Aero Elasticity By SANJANA P U

2. CONTENTS AEROELASTICITY & COLLARS TRIANGLE NECESSITY HISTORY CLASSIFICATIONS PRECAUTIONS FURTHER DEVELOPMENTS

3. INTRODUCTION Aereolasticity is the study of the interaction of inertial, structural and aerodynamic forces on aircraft, buildings, surface vehicles etc. FIGURE : COLLARS TRIANGLE

4. NECESSITY: STUDY OF CATASTROPHIC EFFECTS STUDY OF AERODYNAMIS IN ROTOR DESIGN WIND MILLS & WIND GENERATORS ]   WIND ENERGY INDUSTRY

5. A BIT OF HISTORY: Control surface flutter became a frequent phenomenon during World War-I. It was solved by placing a mass balance around the control surface hinge line

6. HISTORIC EXAMPLES: Handley Page O/ 400 (elevators-fuselage) Junkers JU 90 (fluttered during flight flutter test) P 80 , F 100 , F 14 (transonic aileron buzz) T 46A (servo tab flutter) F 16 , F 18 (external stores LCO, buffeting) F 111 (external stores LCO) F 117 , E- 6 (vertical fin flutter)

7. STATIC DYNAMIC Deals with the static or  steady  response of an elastic body to a fluid flow. Effects:   Divergence   Control reversal   Deals with the body’s  dynamic   response. Effects: Flutter   Buffetting Transonic Aero elasticity AERO ELASTICITY

8. Divergence is a phenomenon in which the elastic twist of the wing suddenly becomes theoretically infinite, typically causing the wing to fail spectacularly. Control reversal is a phenomenon occurring only in wings with  ailerons  or other control surfaces, in which these control surfaces reverse their usual functionality DIVERGENCE: CONTROL REVERSAL: STATIC AEROELASTICITY

9. FLUTTER: Dynamic instability of an elastic structure in a fluid flow. Cause:  positive feedback  between the body's deflection and the force exerted by the fluid flow. DYNAMIC AEROELASTICITY

10. BUFFETING: A high-frequency instability, caused by airflow separation or shock wave oscillations from one object striking another.

11. BUFFETING: CAUSE: Sudden impulse of load increasing. EFFECT: Generally it affects the tail unit of the aircraft structure due to air flow downstream of the wing.

12. TRANSONIC AERO ELASTICITY: A phenenenon that impacts stability of aircraft known as 'transonic dip', in which the flutter speed can get close to flight speed

13. PRECAUTIONS: Aeroelastic Design (Divergence, Flutter, Control Reversal) Wind tunnel testing ( Aeroelastic scaling) Ground Vibration Testing (Complete modal analysis of aircraft structure) Flight Flutter Testing (Demonstrate that flight envelope is flutter free)

14. FUTURE OF AEROELASTICITY Aeroelasticity is a very vibrant research topic. Several improvements to aeroelastic design processes being developed are: –Very large, fully coupled CFD/CSD aeroelastic models – Aeroelastic tailoring –Active aeroelastic structures

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