Post on 08-Nov-2014
Faculty of Engineering Department of Mechanical Engineering
ACOUSTICS & VIBRATION RESEARCH GROUP Pleinlaan 2 • B-1050 Brussel • Belgium
avrg@vub.ac.be • http://avrg.vub.ac.be
Design of improved and advanced aeroelastic models
Rasoul Shirzadeh
Design of improved and advanced aero-elastic models
Short overview of PhD topic
Acoustics & Vibration Research Group
Vrije Universiteit Brussel & Erasmushogeschool Brussel
What is Aeroelasticity?
Aeroelasticity is the study of the interaction of inertial, structural and aerodynamic forces on aircraft, buildings, surface vehicles etc
Design of improved and advanced aero-elastic models 2
Acoustics & Vibration Research Group
Vrije Universiteit Brussel & Erasmushogeschool Brussel
Why is it important?
The interaction between these three forces can cause several undesirable phenomena:
o Flutter
o Divergence o Limit Cycle Oscillations
o Vortex shedding, buffeting, galloping
Design of improved and advanced aero-elastic models 3
Acoustics & Vibration Research Group
Vrije Universiteit Brussel & Erasmushogeschool Brussel
Flutter (dynamic instability) is a growing oscillation of a surface leading to large amplitudes and stresses, and which can lead to structural failure
Design of improved and advanced aero-elastic models 4
Flutter
Example: Tacoma Narrows bridge
Acoustics & Vibration Research Group
Vrije Universiteit Brussel & Erasmushogeschool Brussel
There are two aspects to aeroelastic models
– A structural model – An aerodynamic model
Design of improved and advanced aero-elastic models 5
Aeroelastic Model
In some cases a control model is added to represent the effects of actuators and other control elements
Acoustics & Vibration Research Group
Vrije Universiteit Brussel & Erasmushogeschool Brussel
Simple model that can exhibit true flutter:
Rigid wing + Springs serves as structural model
Example: Theodorsen’s model
Design of improved and advanced aero-elastic models 6
Flutter
Acoustics & Vibration Research Group
Vrije Universiteit Brussel & Erasmushogeschool Brussel
What we are trying to achieve?
To build better aeroelastic models by
o Combining modal analysis and CFD (or even FSI) o Start with simple models
o Develop it for complex models
o Mixed experimental-theoretical approach o improve/update models with experimental data
Design of improved and advanced aero-elastic models 7
Acoustics & Vibration Research Group
Vrije Universiteit Brussel & Erasmushogeschool Brussel
Simple model 1: Vortex shedding
A. Cylinder oscillating cross flow o To investigate frequency lock-in: discrepancies with
literature
B. Fixed cylinder o Reynolds number = 500
o Different turbulence models were tried.
Design of improved and advanced aero-elastic models 8
Acoustics & Vibration Research Group
Vrije Universiteit Brussel & Erasmushogeschool Brussel
Simple model 1: Vortex shedding
Results and open questions
o The drag coefficients are overestimated.
o Agreement of lift coefficients is not perfect.
o Lock-in frequency is not consistent with literature.
o How does OpenFOAM calculate forces? o Which turbulence model is the best choice for our model?
o Is Reynolds number the only parameter (or would results be different for water and air at same Re?)
o What are the sources of these discrepancies?
Design of improved and advanced aero-elastic models 9
Acoustics & Vibration Research Group
Vrije Universiteit Brussel & Erasmushogeschool Brussel
Simple model 2: Theodorsen’s model
o A rigid airfoil which is suspended by two springs, one in plunge and other one in pitch.
o Simplest model that shows true flutter
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wingMotion tutorial case in OpenFOAM
Acoustics & Vibration Research Group
Vrije Universiteit Brussel & Erasmushogeschool Brussel
Simple model 2: Theodorsen’s model
Design of improved and advanced aero-elastic models 11
Questions
o Further analysis required (amplitude, frequency, damping). Is it really flutter?
o Understand the coding of the model in this tutorial.
Faculty of Engineering Department of Mechanical Engineering
ACOUSTICS & VIBRATION RESEARCH GROUP Pleinlaan 2 • B-1050 Brussel • Belgium
avrg@vub.ac.be • http://avrg.vub.ac.be
Any comment/suggestion?
Design of improved and advanced aero-elastic models
Thanks for your attention!