Steady

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.

WeFarm 1.0

Xiaodong Zhang's picture
Submitted by Xiaodong Zhang on May 5, 2015 - 10:39am
Main hypothesis

1. Steady state Atmospheric Boundary Layer flow. Incoming wind velocity profile is based on logarithmic distribution with stratification amendments for non-neutrual conditions. Different from surface layer, the mixing length L is defined as: 1/L = 1/z + 1/Lm + 1 / (zi - z), where z is evelation, zi is thickness of ABL and Lm is a middle length.  

2. No gravity and vertical pressure gradient for neutrual stratification. Potential temperature is adopted for non-neutrual conditions, and a reverse cap is simulated for the convective boundary layer.  

3. A logrithmic profile is used for turbulent flow wall function.  

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.

VestasFOAM 1.1.0 - Steady

Submitted by Yavor Hristov on May 5, 2015 - 12:00am
Main hypothesis

The basis of VestasFOAM is built upon the simpleFoam solver distributed with the publically available OpenFOAM release and suitable for steady, incompressible, turbulent and isothermal flows. This solver and associated k-epsilon turbulence model [2] have been expanded to include appropriate boundary conditions for ABL flow [3], Coriolis force, Durbin realizability constraint [4], extension to stratified flows as wells as canopy [5] and buoyancy source terms. Meshes are automatically generated with Pointwise [6] using structured hyperbolic extrusion ensuring the highest possible quality. In order to reduce the mesh size, the horizontal mesh goes through a step-wise reduction in resolution with height once sufficiently away from the terrain. This creates a hybrid mesh with "hanging-node" type architecture maximizing efficiency without sacrificing mesh quality near the terrain and turbines.

Modified Park

Submitted by Alfredo Peña on May 4, 2015 - 6:07pm
Main hypothesis

The modified Park is a Matlab script version of the Park wake model which takes into account the direct and partial wakes upstream the wind turbine

ISOL RANS 0.1

Submitted by Carlos Peralta on May 4, 2015 - 6:02pm
Main hypothesis

Steady state solver based on OpenFOAM's simpleFoam (version 2.1.1). Isotropic eddy-viscosity turbulence using the Boussinesq approximation, homogeneous forest canopy and actuator disk solver.

GCL

Submitted by Gunner Chr. Larsen on May 4, 2015 - 5:57pm
Main hypothesis

- Steady wind farm flow field based on linear superposition of wake contributions

- Wake contributions based on analytical solution of rotationally symmetric boundary layer equations 

- Turbulence closure: Prandtl's mixing length approach