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Idealized Offshore Low-Level Jets for Turbine Structural Impact Considerations
  • Emily de Jong,
  • Eliot Quon,
  • Daniel Zalkind
Emily de Jong
California Institute of Technology

Corresponding Author:[email protected]

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Eliot Quon
National Renewable Energy Laboratory
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Daniel Zalkind
National Renewable Energy Laboratory
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Abstract

Low level jets (LLJs) describe conditions in which the wind speed reaches a local maximum with respect to altitude near the surface, and have been observed intermittently in the US Mid-Atlantic offshore environment. LLJs pose unique operating conditions for future wind turbines operating in the region, presenting negative shear and locally strong veer, but they are not typically considered in existing turbine standards. This work builds upon recent research that explains the formation and evolution of U.S. Mid-Atlantic LLJs through a simple analytical governing equation. We generate several LLJ inflow conditions with varying jet characteristics based on this analytical model and create monotonically-sheared (MS) analogues with constant veer in order to assess the impacts of the LLJ on turbine performance and loading. Using aeroelastic simulations with these inflow conditions on the IEA 15MW reference turbine, we find that the LLJ leads to a greater range of tower top pitching and yawing moments, which could contribute to larger accumulated structural fatigue in components compared to monotonically-sheared inflow. These preliminary results demonstrate a path toward a unified set of test cases for low-level wind maxima that can inform International Electrotechnical Commission standards related to offshore wind turbine design.