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222 C. Sicot et al. Fig. 40.1. Experimental setup. Note turbulence grid (9%) in nozzle The angle of attack at a given section of the blade is αr = αgeo − αi where αgeo is a geometrical angle and αi the angle induced by the wind turbine wake. Whereas αgeo can be easily measured, αi cannot be measured and has been obtained using a lifting line code developed at the laboratory. 40.3 Results and Discussion 40.3.1 Mean Pressure Values Analysis According to Corten [3], pressure in the separated area is governed, in the ∂p chordwise direction by: ρr∂θ =2vrΩ where Ω is the wind turbine rotational velocity. We assumed that the radial velocity in the separated area, vr, isconstant which leads to a constant chordwise pressure gradient. This assumption has been experimentally validated. Thus, the separated area is defined as the part of the average pressure distribution curve where the slope of the pressure gradient is constant (Fig. 40.2). Tur and αr are, respectively, the local streamwise turbulence level and the local angle of attack on the blade. The pressure gradient and the separation point position, DCp , have been obtained. It has also been observed a stall delay for the greatest turbulence level (Fig. 40.3) as it was observed during tests performed at the laboratory on a non-rotating airfoil [4]. The pressure gradient values measured have been compared with semi- empirical values obtained for a non-turbulent flow ∂Cp r.∂Θ = 4.√ 2.λ 2 r.(λ 2 +( R r )2 ) ([5] on the basis of [3]) (Fig. 40.4). Although semi-empirical results are overestimated, probably because of approximation made on radial velocity, they show the same tendency as the experimental ones. The pressure gradient increases with tip speed ratio and turbulence level. Surface pressure distributions on a rotating and a non-rotating airfoil have been compared (Fig. 40.5). The pressure distribution on the rotating and non-rotating airfoil are similar on the pressure side (attached flow), but a
Cp Xsep/c 1 0.6 0.2 −0.2 −0.6 −1 −1.4 −1.8 −2.2 −2.6 1 0.8 0.6 0.4 0.2 0 0 0.2 0.4 40 Rotation and Turbulence Effects on a HAWT 223 x/c D cp X sep Linear fit 0.6 0.8 1 Separated area Fig. 40.2. Pressure gradient in separated area Tur = 5.9% αr = 11.8˚ Tu = 4.5% Tu = 9% Tu = 12% 0 5 10 15 20 25 30 35 Angle of attack (˚) Fig. 40.3. Turbulence level influence on the separation point position, Xsep
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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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27 Phenomenological Response Theory
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28 Turbulence Correction for Power
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28 Turbulence Correction for Power
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29 Online Modeling of Wind Farm Pow
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29 Online Modeling of Wind Farm Pow
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30 Uncertainty of Wind Energy Estim
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30 Uncertainty of Wind Energy Estim
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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
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Page 221 and 222: 35 Modelling of the Transition Loca
Page 223 and 224: 35 Modelling an Airfoil with Surfac
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Page 227 and 228: 35 Modelling an Airfoil with Surfac
Page 229 and 230: 36 Helicopter Aerodynamics with Emp
Page 235 and 236: 37 Determination of Angle of Attack
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 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
Page 273 and 274: 44 Numerical Simulation of Dynamic
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
Page 289 and 290: 48 Numerical Computations of Wind T
Page 291 and 292: Z X Y 48 Numerical Computations of
Page 293 and 294: References 48 Numerical Computation
Page 295 and 296: 49 Modelling Wind Turbine Wakes wit
Page 297 and 298: U mean / U ref 1 0.9 0.8 0.7 49 Mod
Page 299 and 300: 49.5 Conclusion 49 Modelling Wind T
Page 301 and 302: 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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