Experimental and Numerical Modelling of Flow over Complex Terrain: The Bolund Hill

• Published in: Boundary-layer meteorology 2016-02, Vol.158 (2), p.183-208
• Main Authors: Conan, Boris, Chaudhari, Ashvinkumar, Aubrun, Sandrine, van Beeck, Jeroen, Hämäläinen, Jari, Hellsten, Antti
• Format: Article
• Language: English
• Subjects: Atmosphere; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Atmospherics; Boundary layer; Buildings and facilities; Computer simulation; Earth and Environmental Science; Earth Sciences; Engineering Sciences; Errors; Fluid dynamics; Fluids mechanics; Kinetic energy; Marine; Mathematical models; Mechanics; Meteorology; Modelling; Simulation; Terrain; Tropospheric circulation; Turbines; Wind farms; Wind power; Wind speed; Wind tunnels
• ISSN: 0006-8314; 1573-1472
• DOI: 10.1007/s10546-015-0082-0

In the wind-energy sector, wind-power forecasting, turbine siting, and turbine-design selection are all highly dependent on a precise evaluation of atmospheric wind conditions. On-site measurements provide reliable data; however, in complex terrain and at the scale of a wind farm, local measurements may be insufficient for a detailed site description. On highly variable terrain, numerical models are commonly used but still constitute a challenge regarding simulation and interpretation. We propose a joint state-of-the-art study of two approaches to modelling atmospheric flow over the Bolund hill: a wind-tunnel test and a large-eddy simulation (LES). The approach has the particularity of describing both methods in parallel in order to highlight their similarities and differences. The work provides a first detailed comparison between field measurements, wind-tunnel experiments and numerical simulations. The systematic and quantitative approach used for the comparison contributes to a better understanding of the strengths and weaknesses of each model and, therefore, to their enhancement. Despite fundamental modelling differences, both techniques result in only a 5 % difference in the mean wind speed and 15 % in the turbulent kinetic energy (TKE). The joint comparison makes it possible to identify the most difficult features to model: the near-ground flow and the wake of the hill. When compared to field data, both models reach 11 % error for the mean wind speed, which is close to the best performance reported in the literature. For the TKE, a great improvement is found using the LES model compared to previous studies (20 % error). Wind-tunnel results are in the low range of error when compared to experiments reported previously (40 % error). This comparison highlights the potential of such approaches and gives directions for the improvement of complex flow modelling.