Richard J.A.M. Stevens

Professor at the University of Twente

Wind energy · Turbulence · Environmental flows

Publication 84 · Wind-farm flow

Modeling dynamic wind direction changes in large eddy simulations of wind farms

A. Stieren, S.N. Gadde, R.J.A.M. Stevens, Renewable Energy 170, 1342-1352 (2021).

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Main finding

Rapid wind-direction changes produce wake hysteresis in the tested LES because turbines encounter structures generated under earlier inflow directions. The response magnitude and mechanism do not define general wind-farm laws.

Wind farm power against wind direction for increasing and decreasing rotation
How to read the figure. Wind farm power against wind direction as the direction is rotated at two rates, with separate curves for increasing and decreasing direction and static simulations as reference points. The two curves do not coincide: power at a given direction depends on which direction the wind came from, because the wakes still carry the earlier alignment. The size of that hysteresis is specific to these simulations, not a general wind-farm law. Open the full-resolution figure. Figure 9. A. Stieren et al. (2021). No separate licence is stated here; consult the original publication and credited source before reuse.

Why this matters

Rapid wind-direction changes produce wake hysteresis because turbines encounter structures generated under earlier inflow directions.

Research context

Builds on concurrent-precursor and time-varying-direction methods cited, and on Flow Structure and Turbulence in Wind Farms (read the finding). Complements Modeling space-time correlations of velocity fluctuations in wind farms (read the finding) and Turbulence coherence in wind farms (read the finding) by adding nonstationary direction forcing rather than stationary correlation/coherence.

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