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Alaiz Neutral

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The benchmark is open to participants of the Wakebench project using flow models over topography in neutral conditions. This benchmark is a follow up of the sensitivity analysis (Alaiz_Sensitivity) to validate the results in neutral conditions.


Produce the best estimate of the flow field in neutral conditions above the Alaiz site for the North and South wind directions.

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:

  • Digitized elevation map based on 1:10000 maps (elevation lines every 5 m) and roughness maps based on orthophotos from the Navarra Geoportal (  
  • Coordinates of the mast positions and sensor levels
  • Inlet conditions are not measured. It is up to the user to select the most appropriate profiles. The results will be made independent of this choice by normalizing with the MP5 118 m velocity (U0) and turbulent kinetic energy values (TKE0). A target U0 is 9 m/s and turbulence intensity [6, 10] % for the North and South sectors respectively. 

Validation data

The validation will consist on the following parameters:

  • Velocity ratio with respect to MP5 (U/U0)
  • Ratio of turbulent kinetic energy with respect to MP5 (tke/tke0)

Ensemble averaged profiles for wind direction bin widths of 10º ("validation1") and 30º ("validation2"), for the North and South wind directions and |Fr-1| < 0.2 will be available for the 11 positions of the test site. Besides the mean values, the standard deviation will also be included in order to account for the variability in the ensemble.

Model runs

The user is free to optimize the simulation settings as he/she sees fit. The M3 mesh defined in "Alaiz_Sensitivity" shall be a minimum requirement. The benchmark is carried out in two phases: a blind test without the validation data first and a second round of simulations where the user can optimize the performance by fine-tuning the model settings.

  • Run 1: North (blind)
  • Run 2: South (blind)
  • Run 3: North (fine-tuning)
  • Run 4: South (fine-tuning)

Output data

The requested output data consist of:

  • North-South transect, inlet to outlet boundary, passing by the MP5 position at 40 and 118 m levels (profID = "profNS#")
  • Vertical profiles from ground level to the top of the domain at MP* (profID = "profMP#") and A* (profID ="profA#")

For each output point you should provide: velocity components (U, V, W), turbulence kinetic energy (tke) and eddy viscosity (nu_t). Hence, the required outputs are, in this order: X(m), Y(m), Z(m), U(m/s), V(m/s), W(m/s), tke(m2/s2), nu_t(m2/s).

Use the file naming and format convention described in the Windbench user's guide with profID = prof#, where # = [NS40, NS118, MP1, MP3, MP5, MP6, A1, A2, A3, A4, A5, A6], i.e. 12 output files per user and model run (12x4 = 48 files).


Participants of this benchmark are strongly encouraged to participate in the sensitivity analysis "Alaiz_SensitivityNeutral" in order to be able to identify the sources of uncertainty of the results. At least, justification about grid sensitivity must be provided.

In order to evaluate the added value of model fine-tuning it is important that the user describe how this is performed. Please report on the deviations with respect to the default settings of the blind simulations.

Terms andConditions

Reffer to the Alaiz Test Case guide for the terms and conditions for using the validation datasets.