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Abstract: Wind turbines operate in a very instationary environment, where wind turbines generally
have been modelled with steady airfoil characteristics. The unsteady effects on
the airfoil characteristics influence loads and stability of wind turbines. It is no doubt
that unsteady aerodynamic effect is important to predict aerodynamic damping and
aero-elastic stabilities of wind turbines. Furthermore there is the fact that the size of
wind turbines is getting larger, which cause more unsteadiness on the blades of wind
turbines. In this thesis the effects due to the fluctuation of airfoil will be evaluated for
different reduced frequencies. In order to determine unsteady effects a code has been
developed based on Theodorsen theory and compared with the measurement data of
The Ohio State University. At last, The effects due to the fluctuation on the flapwise
vibration, chordwise vibration and pitch regulation will be evluated at different period
and amplitude of the motion of airfoils.

URI: http://dcoll.jejunu.ac.kr/jsp/common/DcLoOrgPer.jsp?sItemId=000000005999

Table Of Contents: 1 Introduction 8
1.1 Background 8
1.2 The Goal of Research 9
1.3 The Structure of Thesis 9
2 Theoretical Background 11
2.1 Unsteady models 11
2.2 Potential flow 12
2.3 Glauerts Solution for a Thin Airfoil in The Steady Case 13
2.3.1 Zero-thickness Airfoil at Angle of Attack 13
2.3.2 Glauerts Series Expansion Solution 15
2.3.3 Aerodynamic Forces in Terms of Fourier Coefficient in The
Steady Case 17
2.4 Unsteady Flow of a Two-dimensional and Shed Wake Induction Effects 19
2.4.1 Unsteady boundary condition 19
2.4.2 Wake model 20
2.4.3 Solution of Laplace equation 20
2.5 Aerodynamic Forces in Terms of Fourier Coefficient for The Unsteady
Case 23
3 Development of the code and Comparison the Code with Ohio data 26
3.1 Analysis of Unsteady Aerodynamics Performance of Airfoils 26
3.2 Comparison of Modified Theodorsen code with Ohio measurement data 29
3.3 Results of pitching, heaving and vibrating effects on NACA 4415 airfoil 33
3.3.1 Pitching effect 33
3.3.2 Heaving effect 34
3.3.3 Vibrating effect 35
4 Conclusions, recommendations and future works 38
5 Reference 39
6 Appendix 41
A Program description 41
Acknowledgements 48

Citation: 허치훈. (2012). A Study on Effects of Unsteady 2D Aerodynamic Forces and Aero-elastic Stability Based on Theodorsen Theory

Appears in Collections:: Interdisciplinary Programs > Multidisciplinary Graduate School Program for Wind Energy

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