OC5 Project Phase Ib: Validation of Hydrodynamic Loading on a Fixed, Flexible Cylinder for Offshore Wind Applications DeepWind Conference Trondheim, Norway Amy Robertson January 1, 16 NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
Co-Authors Fabian F. Wendt - National Renewable Energy Laboratory, Colorado, USA Jason M. Jonkman - National Renewable Energy Laboratory, Colorado, USA Wojciech Popko - Fraunhofer IWES, Germany Henrik Bredmose Technical University of Denmark, Denmark Michael Borg - Technical University of Denmark, Denmark Flemming Schlutter - Technical University of Denmark, Denmark Jacob Qvist - 4Subsea, Norway Roger Bergua - Alstom Wind, Spain Rob Harries - DNV GL, England Anders Yde - Technical University of Denmark, Denmark Tor Anders Nygaard - Institute for Energy Technology, Norway Luca Oggiano - Institute for Energy Technology, Norway Pauline Bozonnet - IFP Energies nouvelles, France Ludovic Bouy - PRINCIPIA, France Carlos Barrera Sanchez - Universidad de Cantabria IH Cantabria, Spain Raul Guanche García - Universidad de Cantabria IH Cantabria, Spain Erin E. Bachynski - MARINTEK, Norway Ying Tu - Norwegian University of Science and Technology, Norway Ilmas Bayati - Politecnico di Milano, Italy Friedemann Beyer - Stuttgart Wind Energy, University of Stuttgart, Germany Hyunkyoung Shin - University of Ulsan, Korea Matthieu Guerinel - Offshore Renewables, Portugal Tjeerd van der Zee - Knowledge Centre WMC, the Netherlands
IEA Wind Tasks 3 and 3 (OC3/OC4/OC5) Verification and validation of offshore wind modeling tools are need to ensure their accuracy, and give confidence in their usefulness to users. Three research projects were initiated under IEA Wind to address this need: OC3 = Offshore Code Comparison Collaboration (5-9) OC4 = Offshore Code Comparison Collaboration, Continuation (-13) OC5 = Offshore Code Comparison Collaboration, Continuation, with Correlation (14-17) 3
OC5 Project Phases OC3 and OC4 focused on verifying tools (tool-to-tool comparisons) OC5 focuses on validating tools (code-to-data comparisons) Phase I: Monopile - Tank Testing Phase II: Semi - Tank Testing Phase III: Jacket/Tripod Open Ocean 4
OC5 Phase Ib Objective: validate hydrodynamic loads and acceleration response for a fixed, flexible cylinder Test Data from Wave Loads Project: o 3-year project with goal of improving numerical models for wave loads on offshore wind turbines o Carried out collaboratively by DTU Wind Energy, DTU Mechanical Engineering, and DHI o Performed at shallow-water basin at DHI o Thank you to: Ole Petersen at DHI and Henrik Bredmose and Michael Borg at DTU for graciously supplying the data and information needed for this phase of the OC5 project. 5
Test Set-Up 1:8 scale, flexible cylinder On slope to create steep waves Tests done at two water depths:.51 m and.6 m (4 and m full scale) Measurements used: o o o Wave elevation Acceleration at top mass of cylinder Total hydrodynamic force on cylinder 6
Tests Simulated Test # Wave Type Water Depth (m) H/Hs (m) T/Tp (s) Gamma C A C D 1 Regular.51.9 1.5655 1. 1. Regular.51.118 1.5655 1. 1. 3 Irregular.51.4 1.4 3.3 1. 1. 4 Irregular.51.14 1.55 3.3 1. 1. 5 Regular.6.86 1.565 1. 1. 6 Regular.6.11 1.565 1. 1. 7 Irregular.6.133 1.56 3.3 1. 1. 7 Datasets were examined: o o 4 regular cases water depths wave heights 3 irregular cases water depths wave heights First regular wave case used for calibration 7
Summary of Tools and Modeling Approach Participant Code Wave Model (Reg/Irr) Wave Elevation Hydro Model Structural Model Number DOFs 4Subsea OrcaFlex FNPF kinematics FNPF kinematics ME FE, RDS 16 elements 96 DOFs SAMCEF Wind Turbines (S4WT) 5 th Order Stokes/ Linear Airy Stretching ME FE (TS), RD 13 elements 84 DOF DNV GL-ME Bladed 4.6 6 th and 8 th Order SF/ Linear Airy Measured ME FE (TS), MD 8 (CB) DNV GL-PF Bladed 4.6 Linear Airy Measured 1 st Order PF Rigid N/A HAWC 6th and 8th Order SF/L. Airy & FNPF kinematics Stretching & FNPF kin. ME FE (TS), RDS elements, 16 DOF -PF HAWC 6th and 8th Order SF/L. Airy Stretching 1 st Order PF FE (TS), RDS 31 elements, 19 DOF DTU-BEAM OceanWave3D FNPF kinematics FNPF kinematics ME+Rainey FE (EB), RD 16 DOFs IFE 3Dfloat FNPF kinematics FNPF kinematics ME FE (EB), RDS 6 elements, 378 DOF IFE-CFD STAR CCM CFD CFD-derived CFD Rigid N/A IFP-PRI DeeplinesWind 3 rd Ord. SF/ Linear Airy Measured ME FE elements UC-IHC IHVOF FNPF kinematics FNPF kinematics ME Rigid N/A MARINTEK RIFLEX nd Order Stokes & FNPF kinematics Measured & FNPF kin. ME FE(E-B), RDS, FS 167 elements, DOF FAST nd Order Stokes & FNPF kinematics Measured & FNPF kin. ME FE (TS), MD 4 (CB) FAST nd Order Stokes Measured nd Order PF Rigid N/A FEDEM 7.1 Linear Airy None ME FE (EB), RD 13 elements, 84 DOF FEDEM 7.1 5 th Order Stokes None ME FE (EB), RD 13 elements, 84 DOF FEDEM 7.1 Stream Function None ME FE (EB), RD 13 elements, 84 DOF PoliMi POLI-HydroWind nd Order Stokes None ME FE (EB), RD 3 elements, 69 DOF SIMPACK +HydroDyn nd Order Stokes None ME FE (TS), MD 5 UOU UOU + FAST nd Order Stokes None ME Rigid N/A WavecWire nd Order Stokes /Linear Airy Measured nd /1 st Order PF Rigid N/A WMC FOCUS6 (PHATAS) FNPF kinematics FNPF kinematics ME FE (TS), MD 1 (CB) 8
Calibration Group calibrated C A and C D coefficients based on Test 1, to get appropriate levels of force o All participants used same values to have consistency in model parameters to better see differences in modeling approach 1 π D F = CDρDu u + CMρ u 4 Morison s Equation A C A value of 1. was required, which is larger than expected o Suspect the higher measured loads might be due to reflected waves that were not modeled in the simulation 9
Test 1 Regular Wave Deeper Water - Force Results Total force (N) /Hz Total force (N) Test 1,.51 m water depth, H =.9 m, T = 1.5655 s 6 4 - -4 7 7.5 71 71.5 7 7.5 73 73.5 74 74.5 75 Time (s) 8 7 6 5 4 3 -PF IFE-CFD IFP-PRI-elv MARINTEK-kin UOU WMC-kin.5 1 1.5.5 3 Frequency (Hz)
Test 6 Regular Wave Shallower Water - Force Results Test 6,.6 m water depth, H =.86 m. T = 1.565 s Total force (N) /Hz Total force (N) 5-5 - 7 7.5 71 71.5 7 7.5 73 73.5 74 74.5 75 Time (s) 4 3.5 1 1.5.5 3 Frequency (Hz) 11
1 st Peak Force Component Deeper Water Depth WMC-kin UOU MARINTEK-kin IFP-PRI-elv IFE-CFD -PF Test 1,.51 m water depth, H =.9 m, T = 1.5655 s.5 1 1.5.5 3 3.5 4 4.5 Peak Force1 (N) WMC-kin UOU MARINTEK-kin IFP-PRI-elv IFE-CFD -PF Test,.51 m water depth, H =.118 m, T = 1.5655 s.5 1 1.5.5 3 3.5 4 4.5 Peak Force1 (N) Shallower Water Depth Test 5,.6 m water depth, H =.86 m, T = 1.565 s.5 1 1.5.5 3 3.5 4 4.5 Peak Force1 (N) Test 6,.6 m water depth, H =.11 m, T = 1.56 s.5 1 1.5.5 3 3.5 4 4.5 Peak Force1 (N) 1
nd Peak Force Component Deeper Water Depth WMC-kin UOU MARINTEK-kin IFP-PRI-elv IFE-CFD -PF Test 1,.51 m water depth, H =.9 m, T = 1.5655 s.5 1 1.5.5 3 3.5 Peak Force (N) WMC-kin UOU MARINTEK-kin IFP-PRI-elv IFE-CFD -PF Test,.51 m water depth, H =.118 m, T = 1.5655 s.5 1 1.5.5 3 3.5 Peak Force (N) Shallower Water Depth Test 5,.6 m water depth, H =.86 m, T = 1.565 s.5 1 1.5.5 3 3.5 Peak Force (N) Test 6,.6 m water depth, H =.11 m, T = 1.56 s.5 1 1.5.5 3 3.5 Peak Force (N) 13
3 rd Peak Force Component Deeper Water Depth WMC-kin UOU MARINTEK-kin IFP-PRI-elv IFE-CFD -PF Test 1,.51 m water depth, H =.9 m, T = 1.5655 s..4.6.8 1 1. 1.4 1.6 Peak Force3 (N) WMC-kin UOU MARINTEK-kin IFP-PRI-elv IFE-CFD -PF Test,.51 m water depth, H =.118 m, T = 1.5655 s..4.6.8 1 1. 1.4 1.6 Peak Force3 (N) Shallower Water Depth Test 5,.6 m water depth, H =.86 m, T = 1.565 s..4.6.8 1 1. 1.4 1.6 Peak Force3 (N) Test 6,.6 m water depth, H =.11 m, T = 1.56 s..4.6.8 1 1. 1.4 1.6 Peak Force3 (N) 14
Test 7 Irregular Wave Shallower Water. Wave Elev.(m).1 -.1 -. 7 75 7 715 7 75 73 3 Total force (N) - 75 7 715 7 75 73 ) - 7 X-accel at 165 cm (m/s.5 -.5-1 7 75 7 715 7 75 73 Time (s) 15
Irregular Waves Exceedance Probability Plots Test 3 Test 7-1 -1 exceedance - - P P exceedance -PF -3-3 IFP-PRI-elv -4 1 4 3 5 7 6 8 9-4 5 15 Force (N) 5 Force (N) 3 UOU -1 WMC-kin -1 exceedance - - P P exceedance -3-4.1..3.4.5 Acceleration (m/s.6 ).7.8.9-3 -4..4.6.8 1 Acceleration (m/s 1. 1.4 1.6 1.8 ) 16
Conclusions Higher-order wave theory important in capturing higher-order components of hydrodynamic force o Extreme loads o Excitation of structural frequencies o Most important in shallow water Sloped seabed creates complex wave kinematics o Standard wave theories cannot account for slope o CFD-type analysis might be needed to create wave kinematics for nonflat seabed conditions Majority of offshore wind modeling tools do not presently address breaking waves o Complex wave theories and CFD can accurately model steep waves that will break o Need to model the impulsive load that a breaking wave will impart on the structure o Some codes are seeking to include this 17
Thank You! Amy Robertson +1 (33) 384 7157 Amy.Robertson@nrel.gov Operated for the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by Midwest Research Institute Battelle NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.