Comparison of Large Eddy Simulations against measurements from the Lillgrund offshore wind farm

Abstract

Abstract. Numerical simulation tools such as Large Eddy Simulations (LES) have been extensively used in recent years to simulate and analyze turbine-wake interactions within large wind farms. However, to ensure the reliability of the performance and accuracy of such numerical solvers, validation against field measurements is essential. To this end, a measurement campaign is carried out at the Lillgrund offshore wind farm to gather data for the validation of an in-house LES solver. Flow field data is collected from the farm using three long-range WindScanners, along with turbine performance and load measurements from individual turbines. Turbulent inflow conditions are reconstructed from an existing precursor database using a scaling-and-shifting approach, proposed so that the generated inflow statistics match the measurements. Thus, 5 different simulation cases are setup, corresponding to 5 different inflow conditions at the Lillgrund wind farm. Operation of the 48 Siemens 2.3 MW turbines from the Lillgrund wind farm is parameterized in the flow domain using an Aeroelastic Actuator Sector Model (AASM). Time-series turbine performance metrics from the simulated cases are compared against field measurements to evaluate the accuracy of the optimization framework, turbine model and flow solver. In general, results from the numerical solver show good comparison in terms of power production, turbine loading and wake recovery. Nevertheless, larger errors for a few turbines in the wind farm across the simulated cases reveal the need for an improved controller implementation, and possibly a finer simulation grid for capturing wake turbulence.

Sensitivity of Lillgrund Wind Farm Power Performance to Turbine Controller

“…Thus, the flow is always along the x-direction and in practice different wind directions are simulated by rotating the wind farm. Although the used grid is coarse, a grid sensitivity study have revealed that the total power production of the wind farm is not greatly affected by halving the grid size [22].…”

A Data-Driven Reduced Order Model for Rotor Optimization

“…Large Eddy Simulation (LES) (Smagorinsky, 1963) and Detached Eddy Simulations (DES) (Spalart, 1997) studies of isolated rotors have shown to be capable of resolving flow fields relevant for performance and loads of isolated rotors in hover/forward flight (Fitzgibbon et al, 2020), during rotorcraft pitch up maneuvers (Abhishek et al, 2011), and rotor-ship wake interactions (Crozon et al, 2018). In a recent publication by Sood et al (2022), high-fidelity LES simulations were completed for five different inflow conditions of the Lillgrund wind farm. Close comparisons were then drawn between CFD computations and field measurements for turbine power production, loading, and wake recovery.…”

Large-eddy simulations of the interaction between wind farms and mesoscale effects

“…In contrast to infinitely wide wind farms considered in previous studies [12,14,[16][17][18]193], wind farms with a finite spanwise size (see also e.g. [108,110,190,197,208]) are expected to be influenced by entrainment from the sides due to the prevailing wind veer. Wu and Porté-Agel [24] and Allaerts and Meyers [23] assume that a fully developed region might not be reached in various atmospheric conditions even for large wind farms.…”