Aerodynamic calculation of loads and dynamic behavior of wind ...

Contents
Πεξίιεςε .......................................................................................................................... 7
Abstract ............................................................................................................................. 8
1 Introduction ......................................................................................................... 10
1.1 General ........................................................................................................ 10
1.2 Thesis’s objective ........................................................................................ 11
2 The wind resource ............................................................................................... 13
2.1 Wind variations ........................................................................................... 13
2.2 Turbulence intensity .................................................................................... 14
2.3 The boundary layer properties ..................................................................... 16
2.4 The wind velocity as a stochastic process ................................................... 17
2.5 Wind simulation .......................................................................................... 21
3 Aerodynamics of a wind turbine ......................................................................... 27
3.1 Actuator disk concept .................................................................................. 27
3.2 Rotor disk theory ......................................................................................... 33
3.3 An abstract definition of loads’ fundamentals ............................................. 38
3.4 The blade element – momentum (BEM) theory .......................................... 41
3.5 Five significant points concerning B.E.M. .................................................. 44
3.6 An alternative method ................................................................................. 45
3.7 Tower shadow ............................................................................................. 46
4 The algorithm ...................................................................................................... 48
4.1 General ........................................................................................................ 48
4.2 Flow of the algorithm .................................................................................. 48
4.3 Accuracy of the algorithm ........................................................................... 49
5 Results ................................................................................................................. 53
5.1 The two methods of induction factors’ calculation ..................................... 53
5.2 Out-of-plane and in-plane force calculation for constant wind velocity ..... 54
5.3 Generation of wind velocity time histories .................................................. 59
5.4 Generation of aerodynamic-loads time histories ......................................... 64
6 Dynamic Analysis ............................................................................................... 67
6.1 General ........................................................................................................ 67
6.2 Tower model ................................................................................................ 67
6.3 Tower loading .............................................................................................. 70
6.3.1 Displacements ....................................................................................... 70
6.3.2 Stresses .................................................................................................. 76
7 Final remarks and suggestions for further research ............................................. 85
8 References ........................................................................................................... 86
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