Abstract
In this work, we present Large Eddy Simulation (LES) results of atmospheric boundary layer (ABL) flow over complex terrain with neutral stratification using the OpenFOAM-based simulator for on/offshore wind farm applications (SOWFA). The complete work flow to investigate the LES for the ABL over real complex terrain is described including meteorological-tower data analysis, mesh generation and case set-up. New boundary conditions for the lateral and top boundaries are developed and validated to allow inflow and outflow as required in complex terrain simulations. The turbulent inflow data for the terrain simulation is generated using a precursor simulation of a flat and neutral ABL. Conditionally averaged met-tower data is used to specify the conditions for the flat precursor simulation and is also used for comparison with the simulation results of the terrain LES. A qualitative analysis of the simulation results reveals boundary layer separation and recirculation downstream of a prominent ridge that runs across the simulation domain. Comparisons of mean wind speed, standard deviation and direction between the computed results and the conditionally averaged tower data show a reasonable agreement.
Highlights
Wind energy has received increasing attention in recent years as a clean energy alternative to fossil fuels
We present Large Eddy Simulation (LES) results of atmospheric boundary layer (ABL) flow over complex terrain with neutral stratification using the OpenFOAM-based simulator for on/offshore wind farm applications (SOWFA)
For the neutral ABL simulations presented in this work, only the velocity data is taken from the precursor and a zero normal gradient boundary condition is applied for pressure
Summary
Wind energy has received increasing attention in recent years as a clean energy alternative to fossil fuels. On-shore wind farms are often located in complex terrain with hills, ridges and mountain slopes. These topographic features can greatly affect the local flow features such as strong acceleration, separation and recirculation. A detailed wind analysis in the complex terrain is necessary since the flow characteristics have important impacts on the aerodynamic loads and power output of the wind turbines. On-site measurements are increasingly complemented by numerical simulations of the atmospheric boundary layer (ABL) flows to provide more detailed insight into the local flow features [2]. Recent efforts to validate simulation results of flows in complex terrain have struggled due to a lack of available measurement data for that purpose. We present a data analysis from meteorological towers and simulation. The main advantage of using SOWFA is that the underlying CFD library OpenFOAM is designed to handle arbitrary unstructured meshes which might be necessary for complex terrain simulations
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