Investigating turbulence in wind flow over complex terrain

Abstract

Increasing worldwide wind energy production means wind farms are being constructed in areas where the terrain is more complex. Two important features of wind flow over complex terrain are flow separation and anisotropic turbulence. The most commonly used simulation approaches for wind flow use the Reynolds-averaged Navier-Stokes (RANS) equations with a k − ε turbulence closure. A model using this closure has difficulty in estimating separation accurately and cannot represent turbulent anisotropy. In other applications the v^{2}f turbulence closure has shown good ability to predict flow separation. Similarly, the algebraic structure-based turbulence model (ASBM) has shown promise in capturing turbulent anisotropy. In the present study the flow over a representative hill that includes these features is calculated using the RANS equations with both the v2f and ASBM closures. A novel implementation of the ASBM closure is developed allowing a stable, smooth solution to be obtained. The results are compared with experimental data for the same flow, and a good agreement is obtained for the separated region and the Reynolds stress components. Wall functions are developed for the v2f closure to enable the simulation of higher Reynolds number flows both with and without surface roughness. The results are compared with experimental data and are shown to accurately capture the separated region.