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204 W. Geissler et al. References 1. Carr L.W. (1985) Progress in Analysis and Prediction of Dynamic Stall, AIAA, Atmospheric Flight Mech Conf Snowmass Co 2. Carr L.W., Chandrasekhara MS (1996) Compressibility Effects on Dynamic Stall. Prog Aerospace Sci Vol 32 pp 523–573 3. Geissler W. (1993) Instationäres Navier-Stokes Verfahren für beschleunigt bewegteProfilemitAblösung (Unsteady Navier Stokes Code for Accelerated moving Airfoils Including Separation). DLR-FB 92-03 4. Geissler W., Chandrasekhara M.S., Platzer M., Carr L.W. (1997) The Effect of Transition Modelling on the Prediction of Compressible Deep Dynamic Stall, 7th Asian Congress of Fluid Mechanics Chennai (Madras) India 5. Geissler W., Dietz G., Mai H. (2003) Dynamic Stall on a Supercritical Airfoil, 29th European Rotorcraft Forum, Friedrichshafen 6. Geissler W., Dietz G., Mai H., Bosbach J., Richard H. (2005) Dynamic Stall and its Passive Control Investigations on the OA209 Airfoil Section, 31st European Rotorcraft Forum, Florence Italy 7. McCroskey W.J. (1982) Unsteady Airfoils, Ann Rev Fluid Mech Vol 14 pp 285–311 8. Spalart P.R., Allmaras S.R. (1992) A One-Equation Turbulence Model For Aerodynamic Flows, AIAA-Paper 92-0439
37 Determination of Angle of Attack (AOA) for Rotating Blades Wen Zhong Shen, Martin O.L. Hansen and Jens Nørkær Sørensen 37.1 Introduction For a 2D airfoil the angle of attack (AOA) is defined as the geometrical angle between the flow direction and the chord. The concept of AOA is widely used in aero-elastic engineering models (i.e. FLEX and HAWC) as an input to tabulated airfoil data that normally are established through a combination of wind tunnel tests and corrections for the effect of Coriolis and centrifugal forces in a rotating boundary layer. For a rotating blade the flow passing by a blade section is bended due to the rotation of the rotor, and the local flow field is influenced by the bound circulation on the blade. As a further complication, 3D effects from tip and root vortices render a precise definition of the AOA difficult. Today, there exists a lot of experimental and numerical (CFD) data from which precise airfoil data may be extracted. However, this leaves us with the problem of determining lift and drag polars as function of the local AOA. To determine the AOA from e.g. a computed flow field, two techniques have up to now been used. The first technique corresponds to an inverse Blade Element – Momentum (BEM) method in which a measured or computed load distribution is used as input. The technique gives reasonable results and the extracted airfoil data can be tabulated and used for later predictions using the same BEM method. Since the theory is 1D, the accuracy of the extracted airfoil data is restricted to the 1D limitation. Moreover, a BEM code needs a tip correction; different tip corrections results in different airfoil data. The second technique is the averaging technique (AT) employed in [2,3]. This method gives good results, especially in the middle section of a blade. Since the method utilizes averaged data, many input points are needed to evaluate the local flow features. Furthermore, it is difficult to be used for general flow conditions (e.g. at operations in yaw). In consequence, the goal of the paper is to develop a method that can compute correctly the AOA for wind turbines in standard operations and also in general flow conditions.
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Wind Energy Proceedings of the Euro
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Prof. Dr. Joachim Peinke Dr. Stepha
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VI Preface been presented, spanning
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VIII Contents 3.3 Stochastic Wind F
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X Contents 12.6 Subgrid Scale Turbu
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XII Contents 22 Stochastic Small-Sc
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XIV Contents 32 Handling Systems Dr
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XVI Contents 41 3D Numerical Simula
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XVIII Contents 51 Comparing WAsP an
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XX Contents 58.3 Ultra-High Perform
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XXII List of Contributors Lars Berg
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XXIV List of Contributors Renata Gn
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XXVI List of Contributors A. Kiss D
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XXVIII List of Contributors El˙zbi
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XXX List of Contributors Ivo Sláde
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1 Offshore Wind Power Meteorology B
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1 Offshore Wind Power Meteorology 3
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1 Offshore Wind Power Meteorology 5
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2 Wave Loads on Wind-Power Plants i
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Trubaduren 2 Wave Loads on Wind-Pow
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Base moment (10 6 Nm) 0.4 0.2 −0.
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2 Wave Loads on Wind-Power Plants i
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3 Time Domain Comparison of Simulat
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3 Time Domain Comparison Using Cons
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7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 3 T
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4 Mean Wind and Turbulence in the A
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5 Wind Speed Profiles above the Nor
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5 Wind Speed Profiles above the Nor
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Height [m] 100 90 80 70 60 50 40 30
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6 Fundamental Aspects of Fluid Flow
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f Suu(f, z) / σ 2 u(z) 10 0 10 −
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a) c) −0,375 6 Fluid Flow over Co
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7 Models for Computer Simulation of
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y/h 2.5 2 1.5 1 0.5 0 7 Models for
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8 Power Performance via Nacelle Ane
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9 Pollutant Dispersion in Flow Arou
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x1/B 0.3 0.5 0.8 1.0 9 Pollutant Di
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9 Pollutant Dispersion in Flow Arou
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10 On the Atmospheric Flow Modellin
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11 Comparison of Logarithmic Wind P
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Height above ground in m 100 90 80
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12 Turbulence Modelling and Numeric
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13 Gusts in Intermittent Wind Turbu
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Durations (s) 25 20 15 10 5 13 Gust
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14 Report on the Research Project O
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height z (m) 100 80 60 40 20 0 14 R
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14.6 Outlook 14 Report on the Resea
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15 Simulation of Turbulence, Gusts
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S(ƒ)(m/s) 2 /Hz 15 Simulation of T
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15 Simulation of Turbulence, Gusts
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16 Short Time Prediction of Wind Sp
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ms prediction error [m/s] 16 Short
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16 Short Time Prediction of Wind Sp
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17 Wind Extremes and Scales: Multif
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Log10 E(k)*k**(5/3) 6 4 2 0 5/3 cor
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17.3 Discussion and Conclusion 17 W
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18 Boundary-Layer Influence on Extr
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z/H (a) (b) 4 2 18 Boundary-Layer I
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18.6 Concluding Remarks 18 Boundary
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19 The Statistical Distribution of
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19 The Statistical Distribution of
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20 Superposition Model for Atmosphe
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h(u) 0.5 0.3 0.1 20 Superposition M
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21 Extreme Events Under Low-Frequen
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21 Extreme Events Under Low-Frequen
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22 Stochastic Small-Scale Modelling
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p(σ⏐u) 1 0.8 0.6 0.4 0.2 22 Stoc
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22 Stochastic Small-Scale Modelling
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23 Quantitative Estimation of Drift
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24 Scaling Turbulent Atmospheric St
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24 Scaling Turbulent Atmospheric St
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25 Wind Farm Power Fluctuations P.
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25 Wind Farm Power Fluctuations 141
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d rc q rc V 0 q V 25 Wind Farm Powe
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References 25 Wind Farm Power Fluct
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26 Network Perspective of Wind-Powe
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Page 183 and 184: 27 Phenomenological Response Theory
Page 189 and 190: 28 Turbulence Correction for Power
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Page 193 and 194: 29 Online Modeling of Wind Farm Pow
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Page 197 and 198: 30 Uncertainty of Wind Energy Estim
Page 203 and 204: 31 Characterisation of the Power Cu
Page 209 and 210: 32 Handling Systems Driven by Diffe
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Page 213 and 214: 33 Experimental Researches of Chara
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Page 217 and 218: 34 Methodical Failure Detection in
Page 219 and 220: 34 Methodical Failure Detection in
Page 221 and 222: 35 Modelling of the Transition Loca
Page 223 and 224: 35 Modelling an Airfoil with Surfac
Page 225 and 226: (Cl/Cd)max 120 110 100 90 80 70 60
Page 227 and 228: 35 Modelling an Airfoil with Surfac
Page 229 and 230: 36 Helicopter Aerodynamics with Emp
Page 231 and 232: 36 Helicopter Aerodynamics with Emp
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Page 237 and 238: 37 Determination of Angle of Attack
Page 239 and 240: Drag coefficient 0.5 0.4 0.3 0.2 0.
Page 241 and 242: 38 Unsteady Characteristics of Flow
Page 243 and 244: PSD PSD 38 Unsteady Characteristics
Page 245 and 246: 39 Aerodynamic Multi-Criteria Shape
Page 247 and 248: 39 Multi-Criteria Shape Optimizatio
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Page 251 and 252: 40 Rotation and Turbulence Effects
Page 253 and 254: Cp Xsep/c 1 0.6 0.2 −0.2 −0.6
Page 255 and 256: Standard deviation of Cp 0.7 0.6 0.
Page 257 and 258: 41 3D Numerical Simulation and Eval
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Page 261 and 262: 42 Performance of the Risø-B1 Airf
Page 263 and 264: 42 Performance of the Risø-B1 Airf
Page 265 and 266: 43 Aerodynamic Behaviour of a New T
Page 271 and 272: 44 Numerical Simulation of Dynamic
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Page 275 and 276: 45 Modeling of the Far Wake behind
Page 277 and 278: 8 6 uz 4 2 45 Modeling of the Far W
Page 279 and 280: 46 Stability of the Tip Vortices in
Page 281 and 282: 46 Stability of the Tip Vortices in
Page 283 and 284: 47 Modelling Turbulence Intensities
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47 Modelling Turbulence Intensities
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47 Modelling Turbulence Intensities
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48 Numerical Computations of Wind T
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Z X Y 48 Numerical Computations of
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References 48 Numerical Computation
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49 Modelling Wind Turbine Wakes wit
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U mean / U ref 1 0.9 0.8 0.7 49 Mod
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49.5 Conclusion 49 Modelling Wind T
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50 Prediction of Wind Turbine Noise
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0.8 0.6 0.4 0.2 −0.2 −0.4 −0.
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51 Comparing WAsP and Fluent for Hi
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Table 51.1. Measurements and simula
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51 Comparing WAsP and Fluent for Hi
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52 Fatigue Assessment of Truss Join
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53 Advances in Offshore Wind Techno
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Simulation Measurement pitch angle
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53 Advances in Offshore Wind Techno
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54 Benefits of Fatigue Assessment w
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∆σN [N/mm²] 100 10 54 Benefits
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55 Extension of Life Time of Welded
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Transverse residual stresses [N/mm
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56 Damage Detection on Structures o
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56 Damage Detection on Structures o
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57 Influence of the Type and Size o
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[W/m 2 ] q t [W/m 5000 4000 3000 20
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58 High-cycle Fatigue of “Ultra-H
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(a) (b) 450 Load [kN] 400 350 300 2
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59 A Modular Concept for Integrated
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60 Solutions of Details Regarding F
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SR 1000 800 600 400 200 100 80 60 4
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60 Solutions of Details Regarding F
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61 On the Influence of Low-Level Je
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Relative Power and Loading [%] 61 O
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62 Reliability of Wind Turbines Exp
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62 Reliability of Wind Turbines 331
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