Coastal Boundary Layer Development, Impacted by terrain inhomogeneity and non-ideal conditions

Description

The wind is continually affected by the surfaces over which it flows, including the surface roughness. When airflow encounters a roughness change, a turbulent internal boundary layer (IBL) develops, where the flow adjusts to be in equilibrium with the ‘new’ surface. The development and characteristics of the IBL are affected by the terrain morphology and thermodynamic structure of the atmosphere; the IBL’s that tend to most affect the wind are those due to large changes in roughness, such as across coastlines. The scope of this project is to investigate the development of the internal boundary layer downwind of the coastline near Høvsøre, at the Danish National Test Station for wind turbines. The Høvsøre case is of interest due to the presence of a sand dune along the coast. The dune affects the growth of IBL, leading to results that cannot be described by classical IBL models and theory. A three-dimensional representation of the dune will be used as a boundary condition in CFD simulations using the DTU Reynolds-Averaged Navier Stokes (RANS) solver Ellipsys, which is part of the semi-automated wind software WAsP-CFD. Standard wind models (e.g. WAsP) will also be considered. The numerical simulation results and corresponding measurements from Høvsøre will be compared and analyzed. The Høvsøre data include wind and heat flux (stability) measurements at different heights and multiple meteorological masts, and also wind data from the IBL-WiSH project, where multiple ‘WindScanner’ lidars measured the flow downwind of the dunes. The wind modelling is expected to deviate from measurements in some conditions, and limitations of the models will be subsequently investigated. A further understanding of the characteristics and parameters that affect the IBL can benefit Wind Energy in a number of ways. Better estimation of annual energy production can be made in wind climates affected by heterogeneous roughness, e.g. in coastal zones. A better estimation of wind conditions can also lead to more realistic loads estimation for wind turbines. In this project, taking terrain inhomogeneity as a starting point(most real-world sites are affected by such irregularities), the models used will be evaluated and further improvements-corrections will be investigated. This work will hopefully contribute to further understanding of IBLs and their effects on wind energy

Period	4 Jan 2016 → 4 Jul 2016
Examinee	Nikolaos Kouris
Examination held at	Department of Wind Energy
Degree of Recognition	National