The Bolund project was a combined measurement and modeling project related to wind conditions in complex terrain. An isolated steep hill, Bolund, at Roskilde Fjord was equipped with ten measurement masts with conventional meteorological instruments and remote sensing Lidars at several positions for obtaining detailed information of mean wind, wind shear, turbulence intensities etc. The data was gathered in a database for validating advanced flow models.
Background
Numerous numerical codes for the calculation of flow and turbulence over complex terrain exist; from the fast-running linearized Jackson-Hunt type models to many sophisticated non-linear models: RANS, DES, LES, etc. Common for all these are that they use the famous Askervein experiment for verification. The Askervein hill is nearly Gaussian with not too steep slopes. The ambitious goal of the Bolund project was to make a verification experiment over a very steep terrain, The Bolund Experiment, and to use the measurement data as basis for a Blind Comparison of advanced flow models.
The purpose of the Bolund experiment was to develop reliable methods for determining local wind conditions in complex terrains based on remote sensing techniques (Lidar) as well as conventional meteorological instruments in combination with advanced flow computations. Time series of wind speeds and turbulence was collected and analyzed at ten measurement masts equipped with sonics and cup anemometers at several heights together with data from Lidars at several positions. The measurement campaign took place from December 2007 to end of February 2008 and provides the community a comprehensive wind database to be compared with any atmospheric flow model available.
The project included four major tasks:
- Identification of characteristic flow conditions over complex terrain for reliable estimation of power production and wind turbine loads.
- Development of remote sensing techniques for measuring flow conditions in complex terrain including wind shear, turbulence intensities etc., at potential wind turbine positions.
- Application and further validation of advanced Computational Fluid Dynamics (CFD) models for flow over complex terrain.
- A publicly available comprehensive database consisting of experimental data used for evaluation of currently available flow models and methodologies for turbine siting in complex terrain regarding both wind resources and loads.