Neutral

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:

Waving Wheat Neutral

Javier Sanz Rodrigo's picture
Submitted by Javier Sanz Rodrigo on May 4, 2015 - 4:13pm

Scope

The benchmark is open to participants of the Wakebench project using canopy models. This is the first element of the building-block approach in this range, so it should be mandatory if you intend to participate with this model in other test cases down the line.

Objectives

Demonstrate the performance of the model at reproducing the mean flow and turbulent quantities of a horizontally-homogeneous canopy profile.

Data Accessibility

The benchmark is offered to participants of the IEA Task 31 Wakebench who agree with the terms and conditions described below.

Input data

The conditions for simulating the waving wheat canopy profile in neutral conditions are:

  • Free-stream wind speed: U0 = 10.2 m/s
  • Canopy height: hc = 0.047 m
  • Canopy drag coefficient: Cd = 0.68
  • Canopy-area-density: A = 0.1 m-1
  • Obukhov length: L0 = ∞
  • Use dry air with a density ρ = 1.225 kg/m3 and dynamic viscosity μ = 1.73e-5 kg/ms

Validation data

The validation consists on mean and standard deviation values for the horizontal wind speed (U) and mean values of the shear stress (uw).

Model runs

The user is free to define the computational domain and model settings that best fit with the validation data.

Sexbierum Single Wake Neutral

Submitted by Matthew Churchfield on May 4, 2015 - 4:12pm

Scope

The benchmark is open to participants of the Wakebench project using wake and, possibly, atmospheric boundary layer models. This is a realistic wake case measured at the Dutch Experimental Wind Farm at Sexbierum.  It focuses on the single wake case, which is a good “building-block” to the double wake case (Sexbierum_DoubleWakeNeutral).

Objectives

Demonstrate how wake models perform and capture the wake formation and evolution process in the presence of atmospheric shear and turbulence.

Data Accessibility

The benchmark is offered to participants of the IEA Task 31 Wakebench.

Input data

The conditions for simulating the Sexbierum double wake are:

Sexbierum Double Wake Neutral

Submitted by Matthew Churchfield on May 4, 2015 - 4:10pm

Scope

The benchmark is open to participants of the Wakebench project using wake and, possibly, atmospheric boundary layer models. This is a realistic wake case measured at the Dutch Experimental Wind Farm at Sexbierum that has the added complexity of multiple wake interaction. It should test a wake model’s ability to reproduce the wake merging process.

This benchmark follows the single-wake case (Sexbierum_SingleWakeNeutral). Participants are strongly encouraged to participate in both exercises for a more complete model evaluation.

Objectives

Demonstrate how wake models perform and capture the wake merging process in the presence of atmospheric shear and turbulence.

Data Accessibility

The benchmark is offered to participants of the IEA Task 31 Wakebench.

Input data

The conditions for simulating the Sexbierum double wake are:

Norrekaer Enge Data Qualification

Submitted by Kurt Schaldemos... on May 4, 2015 - 4:04pm

Scope

The benchmark is open to participants of Wakebench who want to qualify wind farm measurements for wake model validation.

Objectives

The main objective is to qualify wind farm measurements before data analysis can be performed. The qualification includes an analysis of the wind farm surroundings to identify potential terrain effects and obstacles, which can influence the local flow conditions. The data qualification includes basic quality screening, identification of outliers, and qualification of power values for each wind turbine. This process is used to eliminate sequences where the wind turbines have been stopped or been in an idling mode, start sequence, stop sequence or failure mode.  The data qualification analysis includes to definition of quality-checked references of wind speed and direction.

Data Accessibility

The benchmark is offered to all participants of the IEA Task 31 Wakebench.

Input data

Approximately one year of 10-minute statistics for power and wind measurements recorded in a 42 x 300 kW wind farm have been made available for this benchmark.

The recordings are available in three different formats:

1)       Stored in a MySQL database made accessible through the Internet;
2)       Stored in MS-EXCEL tables or
3)       Stored in a MS-DBASE database.

Norrekaer Enge Power Deficit 1

Submitted by Kurt Schaldemos... on May 4, 2015 - 4:02pm

Scope

The benchmark is open to participants of Wakebench who want to analyze wind farm measurements for wake model validation.

Objectives

Determination of power deficit between pairs of turbines in the wind farm as function of flow direction.

Data Accessibility

The benchmark is offered to all participants of the IEA Task 31 Wakebench.

Input data

Approximately one year of 10-minute statistics for power and wind measurements recorded in a 42 x 300 kW wind farm have been made available for this benchmark.

Validation data

  1. Determine the power deficit between a pair of wind turbines with 6.3 D spacing for a 20 deg inflow sector. The deficit between turbines A2 and A1 is determined for the inflow sector 155-175 deg for a 5° moving window and wind speed interval of 6 – 12 m/s with reference to M1. Power deficit = 1 - Power(A2)/Power(A1)

Model runs

Not applicable 

Norrekaer Enge Power Deficit 2

Submitted by Kurt Schaldemos... on May 4, 2015 - 4:00pm

Scope

The benchmark is open to participants of Wakebench who want to analyze wind farm measurements for wake model validation. 

Objectives

is to determine power deficit along straight rows of turbines in the wind farm. The turbines in flow sector 165 deg  has a constant spacing of 6.3D, while the spacing in direction 257 deg is constant and equal to 8.2D except for a large gap of 26.7D where speed recovery is to be expected.

Data Accessibility

The benchmark is offered to all participants of the IEA Task 31 Wakebench.

Input data

Approximately one year of 10-minute statistics for power and wind measurements recorded in a 42 x 300 kW wind farm have been made available for this benchmark. The following inflow conditions will be considered:

  • Wind speed interval: 9 – 11 m/s;
  • Turbulence intensity: all
  • Flow sectors: 155-175º and 247-267º

Validation data

  1. Power deficit along 6 distinct rows (A, B, C, D, E & F) determined as function of spacing for a direction of 165º with reference to M1.
  2. Power deficit along 7 distinct rows (A1-F1, A2-F2, A3-F3, A4-F4, A5-F5, A6-F6 & A6-F6) determined as function of internal spacing for a direction 257º with reference to M1.

Power deficit = 1 - Power(A2)/Power(A1)

Monin Obukhov Neutral

Javier Sanz Rodrigo's picture
Submitted by Javier Sanz Rodrigo on May 4, 2015 - 3:58pm

Scope

The benchmark is open to participants of the Wakebench project using surface layer models. This is the first element of the building-block approach so it should be mandatory if you intend to participate in other test cases down the line.

The benchmark consists on empty domain (flat terrain) simulations of the neutral surface boundary layer in steady-state conditions. 

Objectives

Demonstrate that the flow model, when run in M-O conditions, is able to reproduce the analytical expressions of the profiles predicted by the theory for neutral conditions. At the same time, it will be possible to check the compatibility of the wall treatment with the flow model for a range of surface roughness conditions.

Data Accessibility

The benchmark is offered to participants of the IEA Task 31 Wakebench. In the future it will be open for public access.

Input data

The conditions for simulating the M-O profiles in neutral conditions are:

  • von karman constant: κ = 0.4

  • Roughness length: z0 = [0.0002, 0.03, 0.4] m

  • Obukhov length: L = ∞

  • Use dry air with a density ρ = 1.225 kg/m3 and dynamic viscosity μ = 1.73e-5 kg/ms

Validation data

The validation data will consist on normalized M-O profiles obtained from analytical functions.

Lillgrund Direction

Submitted by Matthew Churchfield on May 4, 2015 - 3:54pm

Scope

This document outlines three separate components of this benchmark.  It is the hope that the participant will simulate all three components, but the participant is free to simulate any or all of the components.

This benchmark is open to participants of the Wakebench project using wake and, possibly, atmospheric boundary layer models. This is based on the actual operational Lillgrund wind farm in which there are multiple turbines interacting within an array.  The benchmark aims to test a wake/atmospheric model to reproduce the power production observed at Lillgrund when wind is from a southwesterly, southeasterly, and northwesterly sector. 

For the Southwest case, the sector is centered upon 222° aligned with rows A-H in which there is 4.3 rotor diameter (D) spacing.  For the Southeast case, the sector is centered upon 120° aligned with rows 1-8 in which there is a 3.3 D spacing.  For the Northwest case, the sector is centered upon the 300° direction aligned again with rows 1-8, with flow coming from the opposite direction of the Southeast case, with a 3.3 D spacing.

Lillgrund 360 Efficiency

Submitted by Matthew Churchfield on May 4, 2015 - 3:12pm

Scope

The benchmark is open to participants of the Wakebench project using wake and, possibly, atmospheric boundary layer models. This is a case based on the actual operational Lillgrund wind farm in which there are multiple turbines interacting within an array.  This benchmark aims to test a wake/atmospheric model to reproduce the wind plant efficiency observed at Lillgrund over the full wind rose.

Objectives

Demonstrate how wake models perform and capture the wake formation and merging process in the presence of atmospheric shear and turbulence within a large modern wind farm composed of modern multimegawatt turbines. 

Data Accessibility

Brief description about the accessibility of the data

Input data

The conditions for simulating the Lillgrund_360_Efficiency case are: