ABL layer

FITNAH-3D

Christian Wetzel's picture
Submitted by Christian Wetzel on June 11, 2018 - 11:38am
Main hypothesis

FITNAH (Flow over Irregular Terrain with Natural and Anthropogenic Heat sources) has been developed mainly at the Leibniz Universität Hannover, Germany as a mesoscale model. It is applied in the area of wind energy, urban climate and environmental meteorology. For about twenty years FITNAH is used for wind energy site assessment and wind potential mapping by GEO-NET Umweltconsulting GmbH.

DAVM EV

Nicholas Robinson's picture
Submitted by Nicholas Robinson on May 12, 2016 - 4:09pm
Main hypothesis

Uses maximum of eddy-viscosity wake model and a boundary layer wake model at each turbine for each case or timestep.

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.

Alaiz Sensitivity

Javier Sanz Rodrigo's picture
Submitted by Javier Sanz Rodrigo on May 7, 2015 - 10:22am

Scope

The benchmark is open to participants of the Wakebench project using flow models over topography in neutral conditions. This initial benchmark will carry out an assessment of the sensitivity to modeling criteria that is adopted when approaching the simulation of a realistic site for wind farms in complex terrain. In order to simplify the analysis, only the North and South wind direction sectors will be analyzed.

Objectives

Carry out sensitivity tests on different elements of the modeling chain that require user-dependent decisions: domain dimensions, mesh type and resolution, roughness definition, and wind direction binning (1).

Data Accessibility

The benchmark is offered to participants of the IEA Task 31 Wakebench who has signed the NDA attached to the test case guide.

Input data

The conditions for simulating the Alaiz flow field in neutral conditions are:

flapFOAM RANS

Submitted by Jonas Schmidt on May 5, 2015 - 10:53am
Main hypothesis

12 RANS simulations of a uniform non-rotating actuator disk were carried out using OpenFOAM version 2.1.1, with k-e turbulence model including additional dissipation near the rotor, a la El-Kasmi and Masson 2008. These 12 simulations form a data base, from which the wake deficit data is interpolated at arbitrary inflow velocities at hub height. This way CFD simulations are used to define a numerical wake model. flapFOAM is a new wind farm modelling software that is currently in development at Fraunhofer IWES.

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.