The spectral velocity tensor in moderately complex terrain

The purpose of this work is to develop a model of the spectral velocity–tensor in neutral flow over complex terrain (orography and variable roughness). In other words, the influence of hills and roughness changes on spectra, cross-spectra and coherences of relevance for wind engineering is modeled. The resulting equations are implemented in a computer code using the mean flow generated by a linear mean flow model as input. It estimates turbulence structure over hills (except on the lee side if recirculation is present) in the so-called outer layer and also models the changes in turbulence statistics in the vicinity roughness changes. Comparison of the model with atmospheric data shows a reasonable agreement. However, there is certainly room for improvements. The modeled turbulence statistics or simulated fields are suitable as input for dynamic load calculations on wind turbines and other tall structures and is under implementation in the collection of programs called WAsP Engineering.