Numerical modelling of the wind over forests: roughness versus canopy drag

• Main Authors: A. Sogachev, D. Cavar, M. Kelly, E. Dellwik, T. Klaas, P. Kühn
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-06-01
• Series: Advances in Science and Research
• Online Access: https://asr.copernicus.org/articles/17/53/2020/asr-17-53-2020.pdf

<p>Parameterizing the effect of vertically-distributed vegetation through an effective roughness (<span class="inline-formula"><i>z</i>_0,eff</span>) – whereby momentum loss through a three-dimensional foliage volume is represented as momentum loss over an area at one vertical level – can facilitate the use of forest data in flow models, to any level of detail, and simultaneously reduce computational cost. Results of numerical experiments and comparison with observations show that a modelling approach based on <span class="inline-formula"><i>z</i>_0,eff</span> can estimate wind speed and turbulence levels over forested areas, at heights of interest for wind energy applications (<span class="inline-formula">∼60</span>&thinsp;m and higher), but only above flat terrain. Caution must be exercised in the application of such a model to zones of forest edges. Advanced flow models capable of incorporating local (distributed) drag forces are recommended for complex terrain covered by forest.</p>