We use several Large-Eddy Simulation (LES) codes for the comparison with high-fidelity simulations.



SP-Wind is a wind-farm LES code from KUL built on a fully parallelized pseudo-spectral flow solver developed over the last 8 years at KUL. The efficient methods in this code make it a unique platform allowing the simulation of full wind farms and the atmospheric boundary layer during many hours of operation, yielding detailed spatiotemporal velocity fields (typical spatial resolution of 15m and time resolution of 1 second). The code contains atmospheric stratification effects, Coriolis forces, and generates realistic turbulent inflow conditions using concurrent precursor simulations. Wind turbines are included with actuator disk or actuator-line models, and further parametrized with a nonlinear flexible multi-body model that is simulated in a two-way coupled framework at a much higher time resolution.


EllipSys3D is a general purpose 3D flow solver, developed at DTU. The code solves the discretized incompressible Navier-Stokes equations in general curvilinear coordinates using a block structured finite volume approach. EllipSys3D is formulated in primitive variables (pressure-velocity) in a non-staggered grid arrangement. The pressure correction equation is solved using the SIMPLE algorithm and pressure decoupling is avoided using the Rhie/Chow interpolation technique.


HAWC2 is a state-of-the-art aeroelastic code developed at DTU, which simulates wind turbine response in the time domain. The structural part of the code is based on a multi-body formulation using the floating frame of reference method. The wind turbine main structures are subdivided into a number of bodies, where each body is an assembly of Timoshenko beam elements or, alternatively, a super element determined from a detailed FEM model. The bodies are connected by kinematic constraints formulated as algebraic equations, which impose limitations of the bodies’ motion. External forces are placed on the structure in the deformed state. The aerodynamic part of the code is based on the blade element momentum (BEM) theory, but extended from the classic approach to handle dynamic inflow, dynamic stall, skew inflow, shear effects on the induction and effects from large deflections. The code has been extensively validated during the last decade and is used in both industry and academia.


SOWFA is a WPP simulator developed by NREL. It models flow via CFD (OpenFOAM) using a Large Eddy Simulator (LES) approach. The turbine is modelled as an actuator line, which in turn is resolved using the aeroelastic tool FAST. This coupling enables a high fidelity resolution of the flow interactions among individual turbines in the WPP. FAST is a public domain multibody aeroelastic simulator for wind turbines developed by NREL. The tool has been successfully tested in several validation exercises providing good results against similar tools.


The Dynamic Wake Meandering model (DWM) is a medium-fidelity model providing detailed information of the non-stationary inflow wind field to each individual wind turbine within a WPP. The model describes the essential physics of the problem and accounts both for the observed increased turbulence level of wake affected flow fields and for the modified turbulence structure of such. The core of the model is a split of turbulence scales, with large scales being responsible for stochastic wake meandering, and small scales being responsible for wake attenuation and expansion in the meandering frame of reference as caused by turbulent mixing.


Fuga is an extremely fast CFD RANS model for the prediction of energy production in wind farms taking wake effects into account. Being based on a linearization of the NS equations and written in a standard form based on a mixed spectral formulation, the model is approximately one million times faster than a conventional CFD RANS codes. A new solution method is used to solve the equations, which involves intensive use of lookup tables for storage of intermediate results.
17 DECEMBER 2018