Abstract
Currently, the state of the art in wind farm flow physics modeling are Large Eddy Simulations (LES) which resolve a large part of the spectra of the turbulent fluctuations. But this type of model requires extensive computational resources. One wind speed and direction simulation of the Lillgrund wind farm can take between 160k and 3000k processor hours depending on how the turbines are modeled [1, 2]. The next-fidelity model types are Reynolds-Averaged Navier-Stokes (RANS) models which resolve only the mean quantities and model the effect of turbulence fluctuations. These models require about two orders of magnitude less computational time, but generally do not produce accurate predictions of the mean flow field. Proposed modifications made to these models so far do not generalize well and there is room for improvement. Hence, we present the first steps towards using a data-driven approach to aid in deriving new RANS models that generalize well to different turbine types, varying atmospheric stability, and farm layouts. To do so, time-averaged LES data is used to derive corrections to existing RANS models. The approach uses a deterministic symbolic regression method to infer algebraic correction terms to the RANS turbulence transport equations. Optimal correction terms to the RANS equations are derived using a frozen approach where time-averaged flow fields from LES are injected into the RANS equations. The potential of the approach is demonstrated under neutral conditions for multi-turbine constellations at wind-tunnel scale. The results show promise, but more work is necessary to realize the full potential of the approach.
Highlights
Offshore wind farms have the potential to become the sustainable future power plants of NorthWestern Europe
There exist a multitude of models that attempt to model wake effects varying in physical fidelity, accuracy and computational cost, ranging from simple engineering models to complex computational fluid dynamics codes [3]
State of the art are Large Eddy Simulations (LES) which is a high fidelity Computational Fluid Dynamics (CFD) method where most of the turbulent scales are resolved with the remaining ones modeled
Summary
Offshore wind farms have the potential to become the sustainable future power plants of NorthWestern Europe. The Dutch government projects a growth towards 11.5 GW of installed offshore capacity in 2030, entailing that a large part of the North Sea will be filled with wind farms. There exist a multitude of models that attempt to model wake effects varying in physical fidelity, accuracy and computational cost, ranging from simple engineering models to complex computational fluid dynamics codes [3]. State of the art are Large Eddy Simulations (LES) which is a high fidelity Computational Fluid Dynamics (CFD) method where most of the turbulent scales are resolved with the remaining ones modeled. Reynolds-Averaged Navier-Stokes (RANS) models are much faster because they model all scales resulting in coarser meshes and direct equations for the mean quantities without a need for time-averaging of the simulation. Sometimes transient quantities are of interest and the atmospheric boundary layer is inherently transient, but RANS models can still provide useful information for time-averaged
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