Experimental characterization of wind turbine wakes: Wind tunnel tests and wind LiDAR measurements

• Linear stability analysis of wind turbine wakes performed on wind tunnel velocity measurements
• 3D reconstruction of the hub vortex instability as single-helix counter-winding unstable mode
• Volumetric LiDAR measurements of wakes produced by utility-scale wind turbines
• Wind turbine wakes recover faster under convective thermal stability regimes than for neutral conditions
• The hub vortex instability is promoted under neutral and stable thermal stability regimes than for convective conditions.
• A facile one-step growth of Co3O4 nanopillar arrays on 3D hierarchical N-doped carbonized wing scale. (CWs-Co3O4)
• CWs-Co3O4 could be directly used as binder-free electrode for supercapacitors.
• The performance of supercapacitors depends on the N-doped and 3D ordered periodic channel architecture.
• The supercapacitors based on CWs-Co3O4 showed high specific capacity of 978.9 F
• g-1.

The characterization of wind turbine wakes produced for different loading conditions of the turbine and incoming wind is a crucial task for design of wind farm layout. Indeed, the optimization of the power harvested from a wind farm can only be achieved if detrimental wake interactions are carefully inhibited or mitigated. In this paper the importance of performing wind turbine wake measurements is emphasized through two experiments, which are complementary for the experimental measurement techniques used and scientific results achieved. First, wind tunnel tests of a down-scaled wind turbine are presented, for which fixed-point turbulence measurements are leveraged to predict the hub vortex instability encountered in the near wake. The second experiment consists in wind LiDAR measurements of the wake produced by a utility-scale wind turbine under different regimes of the atmospheric thermal stability. It is shown that wind turbine wakes recover faster under convective conditions than for neutral ones.

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