Effect of low-level jet height on wind farm performance

Gadde, S.N.; Stevens, R.J.A.M.

doi:10.1063/5.0026232

Publication 85 · Atmospheric turbulence

Effect of low-level jet height on wind farm performance

S.N. Gadde, R.J.A.M. Stevens, J. Renew. Sustain. Energy 13, 013305 (2021).

Read the article Open-access version (university repository)

Featured article by the Journal of Renewable and Sustainable Energy.

Main finding

The article asks how a fixed stable-boundary-layer LLJ behaves when it lies above, across, or below a farm's rotor-swept area. Boussinesq LES uses a Lagrangian dynamic SGS closure, Monin–Obukhov wall fluxes, filtered actuator disks, concurrent precursor inflow, two-direction fringe layers, Rayleigh damping, and local turbine yaw control. The moderately stable inflow has G=8 m s^-1, f=1.159e-4 s^-1, offshore z_0=0.002 m, surface cooling 0.5 K h^-1, z_i=131.6 m, z_jet approximately 125 m, u_jet/G=1.21, and z_i/L=2.95.

Energy budget per turbine row for low-level jets above, at, and below hub height — **How to read the figure.** Row-by-row energy budget for a wind farm under a stable-boundary-layer low-level jet placed above, across, and below the rotor, with the integrated entrainment flux for all three cases in the final panel. The entrainment term changes sign between cases: energy reaches the turbines from above when the jet sits above the rotor and from below when it sits beneath it. Figure 5 gives the row-averaged power that follows. Open the full-resolution figure. Figure 7. S.N. Gadde and R.J.A.M. Stevens (2021). No separate licence is stated here; consult the original publication and credited source before reuse.

Why this matters

The principal lesson is that energy can reach a farm from above or below depending on LLJ position.

Research context

The introduction reverses the inequalities in its numbered scenario list. The figure, method, results, and conclusion consistently use the physically correct definitions: the jet is above the rotor when its height exceeds hub height and below it when the inequality is reversed.

Coverage of this research

AIP Publishing — Low-Level Jets Create Winds of Change for Turbines, 23 February 2021. Publisher release on the Gadde–Stevens study of jet height and wind-farm performance.

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