Numerical Study of the Effect of Unsteady Aerodynamic Forces on the Fatigue Load of Yawed Wind Turbines
The intentional yaw offset of wind turbines has shown potential to redirect wakes, enhancing overall plant power production, but it may increase fatigue loading on turbine components. This study analyzed fatigue loads on the NREL 5 MW reference wind turbine under varying yaw offsets using blade elem...
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2025-07-01
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| author | Dereje Haile Hirgeto Guo-Wei Qian Xuan-Yi Zhou Wei Wang |
| author_facet | Dereje Haile Hirgeto Guo-Wei Qian Xuan-Yi Zhou Wei Wang |
| author_sort | Dereje Haile Hirgeto |
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| description | The intentional yaw offset of wind turbines has shown potential to redirect wakes, enhancing overall plant power production, but it may increase fatigue loading on turbine components. This study analyzed fatigue loads on the NREL 5 MW reference wind turbine under varying yaw offsets using blade element momentum theory, dynamic blade element momentum, and the converging Lagrange filaments vortex method, all implemented in OpenFAST. Simulations employed yaw angles from −40° to 40°, with turbulent inflow generated by TurbSim, an OpenFAST tool for realistic wind conditions. Fatigue loads were calculated according to IEC 61400-1 design load case 1.2 standards, using thirty simulations per yaw angle across five wind speed bins. Damage equivalent load was evaluated via rainflow counting, Miner’s rule, and Goodman correction. Results showed that the free vortex method, by modeling unsteady aerodynamic forces, yielded distinct differences in damage equivalent load compared to the blade element method in yawed conditions. The free vortex method predicted lower damage equivalent load for the low-speed shaft bending moment at negative yaw offsets, attributed to its improved handling of unsteady effects that reduce load variations. Conversely, for yaw offsets above 20°, the free vortex method indicated higher damage equivalent for low-speed shaft torque, reflecting its accurate capture of dynamic inflow and unsteady loading. These findings highlight the critical role of unsteady aerodynamics in fatigue load predictions and demonstrate the free vortex method’s value within OpenFAST for realistic damage equivalent load estimates in yawed turbines. The results emphasize the need to incorporate unsteady aerodynamic models like the free vortex method to accurately assess yaw offset impacts on wind turbine component fatigue. |
| format | Article |
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| institution | Kabale University |
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| spelling | doaj-art-768789a41ba14aaa8a5f97378b292ce82025-08-20T03:32:32ZengMDPI AGMachines2075-17022025-07-0113760710.3390/machines13070607Numerical Study of the Effect of Unsteady Aerodynamic Forces on the Fatigue Load of Yawed Wind TurbinesDereje Haile Hirgeto0Guo-Wei Qian1Xuan-Yi Zhou2Wei Wang3State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, ChinaSouthern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Ocean Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, ChinaState Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, ChinaState Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, ChinaThe intentional yaw offset of wind turbines has shown potential to redirect wakes, enhancing overall plant power production, but it may increase fatigue loading on turbine components. This study analyzed fatigue loads on the NREL 5 MW reference wind turbine under varying yaw offsets using blade element momentum theory, dynamic blade element momentum, and the converging Lagrange filaments vortex method, all implemented in OpenFAST. Simulations employed yaw angles from −40° to 40°, with turbulent inflow generated by TurbSim, an OpenFAST tool for realistic wind conditions. Fatigue loads were calculated according to IEC 61400-1 design load case 1.2 standards, using thirty simulations per yaw angle across five wind speed bins. Damage equivalent load was evaluated via rainflow counting, Miner’s rule, and Goodman correction. Results showed that the free vortex method, by modeling unsteady aerodynamic forces, yielded distinct differences in damage equivalent load compared to the blade element method in yawed conditions. The free vortex method predicted lower damage equivalent load for the low-speed shaft bending moment at negative yaw offsets, attributed to its improved handling of unsteady effects that reduce load variations. Conversely, for yaw offsets above 20°, the free vortex method indicated higher damage equivalent for low-speed shaft torque, reflecting its accurate capture of dynamic inflow and unsteady loading. These findings highlight the critical role of unsteady aerodynamics in fatigue load predictions and demonstrate the free vortex method’s value within OpenFAST for realistic damage equivalent load estimates in yawed turbines. The results emphasize the need to incorporate unsteady aerodynamic models like the free vortex method to accurately assess yaw offset impacts on wind turbine component fatigue.https://www.mdpi.com/2075-1702/13/7/607fatigue loadyaw offsetunsteady aerodynamic forceswind turbine aeroelastic response |
| spellingShingle | Dereje Haile Hirgeto Guo-Wei Qian Xuan-Yi Zhou Wei Wang Numerical Study of the Effect of Unsteady Aerodynamic Forces on the Fatigue Load of Yawed Wind Turbines Machines fatigue load yaw offset unsteady aerodynamic forces wind turbine aeroelastic response |
| title | Numerical Study of the Effect of Unsteady Aerodynamic Forces on the Fatigue Load of Yawed Wind Turbines |
| title_full | Numerical Study of the Effect of Unsteady Aerodynamic Forces on the Fatigue Load of Yawed Wind Turbines |
| title_fullStr | Numerical Study of the Effect of Unsteady Aerodynamic Forces on the Fatigue Load of Yawed Wind Turbines |
| title_full_unstemmed | Numerical Study of the Effect of Unsteady Aerodynamic Forces on the Fatigue Load of Yawed Wind Turbines |
| title_short | Numerical Study of the Effect of Unsteady Aerodynamic Forces on the Fatigue Load of Yawed Wind Turbines |
| title_sort | numerical study of the effect of unsteady aerodynamic forces on the fatigue load of yawed wind turbines |
| topic | fatigue load yaw offset unsteady aerodynamic forces wind turbine aeroelastic response |
| url | https://www.mdpi.com/2075-1702/13/7/607 |
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