Physical Modeling and CFD Simulation of Wave Slamming on Offshore Wind

Transcription

1 Physical Modeling and CFD Simulation of Wave Slamming on Offshore Wind Turbine Structures Arndt Hildebrandt d Franzius-Institute for Hydraulic, Waterways, and Coastal Engineering Slide 0

2 Overview: Potential & Problems Test field Alpha ventus - RAVE GIGAWIND av Laboratory experiments Numerical simulation Qu uelle: REpow wer Summary & Perspectives Slide 1

3 Project Approved projects in the German area of the North Sea OWEC pilot phase OWEC complete Test field: 6 x Tripods 6 x Jackets Cummulative energy [MW] Distance to shore [km] Water depth [m] Dollart Emden 1 1 4,5 0,01 3 Alpha Ventus (Borkum West I) Sandbank Bard Offshore Dan Tysk Borkum Riffgrund West Borkum Riffgrund Nordsee Ost Butendiek Enova Offshore North Sea Amrumbank West Nördlicher Grund Global Tech I Hochsee Windpark Nordsee Gode Wind Meerwind (Ost und Süd) Hochsee Windpark, He Dreiht Borkum West II Nordergründe Bard Offshore Hooksiel 1 Source: 1 DOTI/Matthias Ibeler, ,4 2-8 Total: 4607 Slide 3

4 Research project GIGAWIND alpha ventus SHM Loads Mass production Corrosion Structure health monitoring v corr Scour Structure soil interaction Dynamic response Holistic design Slide 4

5 = 51 acceleration meters = 113 strain gauges 30 water pressure sensors (WPS) => 2 vertical profiles: 6 and 4 WPS => 1 horizontal profile: 22 WPS Current velocity meter => ADCP + FINO 1 Wave recording => Wave buoy + FINO 1 dz=50 cm dx=78 cm dz=70 cm Video camera => Wave run up Wind data Recording: October 2009 Data: 2010 Slide 6

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7 30 Presssure Sensors (PS) => Vertical profile, 14+4 PS => Horizontal profile with 7 PS => Upper braces with 6 PS 2 Acceleration meters (xyz) 8 Strain gauges Current meters => 2 x 3 NSW probes (xz) Water elevation => 24 Wave gauges Cameras (front-, back view) => Wave runup, wave geometry Slide 9

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10 signal_2_fft η(t * ) = Free water surface in time domain t * = t/δt => t * = 1,2, N N = Number of timestepst Δt in time series a = Amplitude f = Frequency α = Phaseshift fft_2_cfxpre f Slide 12

11 1 Frequency 36 Frequencies Slide 13

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17 Inlet: U max = 4.0 m/s Small curling factor like deep water breaker Pile-up effect Water level gradient at pile during impact Diffusion in area of coarse Snapshot (5.68 s / 8.00 s), H B, x=105m = = 1.5 m mesh Slide 19

18 Inlet: U max = 4.0 m/s Small curling factor like deep water breaker Pile-up effect Water level gradient at pile during impact Diffusion in area of coarse Snapshot ( s / 8.00 s), H B, x=105m = = 1.5 m mesh Slide 20

19 Inlet: U max = 4.0 m/s Small curling factor like deep water breaker Pile-up effect Water level gradient at pile during impact Diffusion in area of coarse Snapshot (6.78 s / 8.00 s), H B, x=105m = = 1.5 m mesh Slide 21

20 Inlet: U max = 4.0 m/s Small curling factor like deep water breaker Pile-up effect Water level gradient at pile during impact T3d_698.cvf Snapshot (6.98 s / 8.00 s), H B, x=105m = = 1.5 m Diffusion in area of coarse mesh Slide 22

21 WKS_Monopile_Sym_3D.cvf Slide 23

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23 Snapshot of the wave profile during wave impact. Partly vertical water front. Case_06a_x_167.cvf Slide 25

24 Pressure at various heights α= =0 α= =15 α= =30 α= =45 Symmetric pressure distribution 30% reduced pressure over 7% of H b in upper zone => curling factor Increasing rise time at lower pressure sensors Slide 26

25 Pressure sensor 22 cm above SWL Symmetric pressure distribution Roughly 250 ms pressure crest Peak value shows 1 kn/m² difference (wave front, heighest sensor position) Slide 27

26 Pressure peak at cylinder front Small area with rapid decrease at the upper limit (small dy) Peak characteristic >30 & < 45 for this point of time (dt < 0.01s) Slide 28

27 Summary & perspective GIGAWIND alpha ventus Wind, shallow waters, renewable Prototype installed Data 2010 Development Physical and numerical modeling, field data Ongoing tests Large Wave Flume (GWK) tests 2010 Efficient design Calibration of numerical models for breaking waves Peak pressure distribution, curling factor, rise time Slide 29

28 Source: Offshore-Stiftung/Multibrid/Jan Oelker, 2009 Thank you for your kind attention! ti Slide 30