Wind-tunnel and field investigation of the effect of local wind direction on speed-up over hills

Measurements of flow past simulated sinusoidal hills were taken in an atmospheric boundary layer wind tunnel (ABLWT) that modeled typical full-scale complex terrain for many wind turbine locations in the Altamont Pass, California, USA. Velocity profiles and speed-up factors for several model hills were determined. All hills modeled had the same height and sinusoidal cross-section, and length-to-width aspect ratios of infinity, four and one. Each of the three models was tested with approach wind directions from 01 to 901, in 151 increments. It was observed that speed-up can vary significantly depending on the approaching wind direction. The effect of wind direction on speed-up was also investigated using field data from a site in the Altamont Pass. Average speed-up factor was found to vary significantly at the site in time, and as a function of atmospheric stability. r 2006 Elsevier Ltd. All rights reserved.