Atmospheric flow over real terrain topography: Numerical simulations against Experimental data and Theoretical models

The application of reduced order models for the estimation of local atmospheric flows in presence of complex terrain topography is challenged by the variety of the terrain geometrical features and of the atmospheric flow parameters. As an example, during the assessment of new wind farm site there is the need to accurately estimate how the terrain topography affects the local flow features and, as a consequence, the Annual Energy Production.

In this study we try to reconcile the theoretical models of flows over rough surfaces with numerical and experimental data of the flow over real terrain topography. We consider the complex terrain of the Perdigão site, in Portugal. This site consists of two parallel ridges with a wind turbine located on the top of one of the ridges. In 2017 a field campaign collected data at several locations. We carried out Large Eddy Simulations of the flow over the site topography and compared them with experimental data. Given the resemblance between the Perdigão site with regular rough surfaces, we can compare data from numerical simulation with theoretical models both at the macroscale level, i.e. the effect of terrain topography on the atmospheric boundary layer, and at the microscale level, i.e. the vegetation that acts as roughness for the local flow.