Open-source

CFDWind2.0

Submitted by Roberto A. Chav... on May 27, 2015 - 12:00am
Main hypothesis

Similar to CFDWind1, this model assumes isotropic eddy-viscosity turbulence,and the two-equation closure scheme (k-ε) modified for atmospheric flows. However, in order to extend the surface layer limitations to the full Atmospheric Boundary Layer (ABL) depth, it is necessary to include Coriolis effects and to limit the growth of turbulence with height, as demonstrated by Detering & Etling (1985).

This is achieved in the k-ε by adopting the Apsley & Castro (1994) correction on the Cε1 constant for neutral conditions.

A simulation of horizontally homogeneous conditions (i.e. a 1D ) is firstly carried out as a precursor simulation in order to define the inlet conditions for the real-terrain run.

CFDWind1.1

Submitted by Roberto A. Chav... on May 27, 2015 - 12:00am
Main hypothesis

This model is formulated with the assumptions of isotropic eddy-viscosity turbulence and the k-ε two-equation closure scheme modified for atmospheric flows.

CFDWind1 deals with surface boundary layer (SBL) by imposing a set of coefficients as well as proper modifications to the boundary conditions (inlet boundary and wall functions) in order to comply with the Monin-Obukhov Similarity Theory (MOST) as proposed by Richards & Hoxey (1993) and Parente et al. (2011). 

CFDWind 1.0

Submitted by Roberto A. Chav... on May 16, 2015 - 12:00am
Main hypothesis

Steady-state, surface layer, isotropic eddy-viscosity turbulence, boussinesq approximation for air density.

In this first version of CFDWind1, the near wall inconsistency was solved by using the Blocken et al. 2007 approach which was inherited from the previous implementation in the commercial solver Fluent, which does not allow to access the source code in order to modify the wall functions.   Further versions (CFDWind1.1 and CFDWind2) have updated this condition to the more consistent formulation of Richards & Hoxey.

WeFarm 2.0

Xiaodong Zhang's picture
Submitted by Xiaodong Zhang on May 5, 2015 - 10:41am
Main hypothesis

Almost the same as WeFarm 1.0, they both are general purpose CFD solvers modified for atmospheric boundary layer flow. This version uses OpenFoam 2.0.7. solve. Other differences with respect to WeFarm 1.0:

1. In the k-ε turbulence model, the model constant = 0.036 based on wind farm measurements.

2. Wall functions based on roughness height Kw are adopted.

SemiParabollicFOAM

Daniel Cabezon's picture
Submitted by Daniel Cabezon on May 5, 2015 - 9:59am
Main hypothesis

The model derives from a previous elliptic model and it is inspired on the parabolic technique of other models such as UPMPARK and Windfarmer but using the actuator disk technique to represent the wind turbine instead of wind speed deficit. 

The wind turbine is represented as an actuator disk uniformly loaded. This means that the wind turbine acts as a sink of momentum, associated to the drag force exerted over the incoming flow. The reference wind speed for each disk is initially calculated from the wind speed at the position of the disk and corrected through the method proposed by Calaf et.al.

The solution algorithm consists of a decomposition of the domain into a finite number of adjacent subdomains that are solved sequentially in the axial direction, using the output of each subdomain as input for the next one. This is done until the end of the domain is reached. This way the computational time becomes significantly lower in comparison to the solution of a single domain by means of a purely elliptic approach.

SOWFA - LES

Submitted by Matthew Churchfield on May 4, 2015 - 6:36pm
Main hypothesis

The large-eddy simulation (LES) solver within the Simulator for On/Offshore Wind Energy (SOWFA) is built upon the Open-source Field Operations And Manipulations (OpenFOAM) computational fluid dynamics (CFD) toolbox.  The solver is incompressible and uses the unstructured finite-volume formulation.  Buoyancy effects are included through a Boussinesq buoyancy forcing term.  Turbines are modeled with actuator lines.