Richard J.A.M. Stevens

Physics of Fluids · University of Twente

Publication 73 · Atmospheric turbulence

Effects of Two-Dimensional Steep Hills on the Performance of Wind Turbines and Wind Farms

L. Liu, R.J.A.M. Stevens, Bound.-Layer Meteorol 176, 251–269 (2020).

Main finding

The paper asks how an idealized steep two-dimensional hill changes power and wakes for a single turbine, an aligned or staggered farm, and a valley-confined farm. It uses truly neutral, pressure-driven wall-modelled LES with a Smagorinsky SGS model, an immersed-boundary hill, and filtered actuator disks (C_T=0.75, C_T'=4/3). Horizontal discretization is pseudo-spectral/periodic; vertical differencing is second order; concurrent precursor inflow is used.

Turbine power relative to flat terrain on the windward and leeward sides of a hill
How to read the figure. Power production, relative to the same turbine in flat terrain, for turbines on the windward (a) and leeward (b) side of a steep two-dimensional hill, sketched above each panel. Turbines high on the windward slope and at the summit gain from terrain speed-up, reaching up to about 2.5 times their flat-terrain reference, while several of the shorter leeward turbines produce less. Whether a whole farm gains is a separate question this figure does not answer. Open the full-resolution figure. Figure 3. L. Liu and R.J.A.M. Stevens (2020). No separate licence is stated here; consult the original publication and credited source before reuse.

Why this matters

It is useful for separating local speed-up from whole-farm performance.

Research context

The response combines hilltop acceleration, windward blockage, lee separation, terrain-following turbine wakes, pressure recovery, and terrain-generated transport. Enhanced vertical flux alone does not guarantee faster wake recovery.

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