Wind Farm Detached-Eddy Simulations Using an Immersed Boundary Method-Actuator Surface Model Solver

Abstract

A comprehensive set of validation cases on wind turbine aerodynamics is numerically investigated using a newly developed immersed boundary method-actuator surface model (IBM-ASM) solver in OpenFOAM. Detached eddy simulations are performed, where the nacelle and tower are represented by the IBM, and the unsteady wind turbine blades are modelled by the ASM. The IBM-ASM solver offers significant advantages over the conventional body-fitted mesh approach in terms of the setup and computational cost because it enbales a simple Cartesian mesh with fully-automated meshing, and the relative motion between the rotating and non-rotating components can be resolved without any mesh deformation. These benefits can be amplified when it comes to a large wind farm simulation which includes a number of wind turbines. The IBM-ASM solver has been extensively validated for various helicopter configurations, and this study will show that the solver can be translated to wind turbine applications with a potential towards computational fluid dynamics simulations of rotorcraft operations in a wind farm. In this study, the validation cases include i) a single New MEXICO wind turbine in a uniform flow, ii) a single model wind turbine with and without the atmospheric boundary layer (ABL) to evaluate the impact of the ABL on the wind turbine wake, where the inflow turbulence is produced by a synthetic turbulence generator based on Mann spectral tensor model, and iii) Lillgrund wind farm simulation to study the wake interaction between wind turbines and its effect on the power production of the wind farm. The simulation outcomes will be compared with experimental measurements, and other numerical study results both quantitatively and qualitatively. Computational expenses will be presented and discussed.