Wind Field Generator Overview

If an unsteady simulation is being carried out, it is necessary to define the wind field. This provides important information for the calculation of aerodynamic quantities. Three types of wind fields can be generated for use in QBlade. These are described individually below.

Uniform Wind Field

A uniform wind field is specified directly within the Wind Input Type of the turbine simulation dialogue, shown in Fig. 88 (see Simulation Module Overview). The necessary input parameters including velocity, horizontal inflow angle and directional shear are defined here. In the case that the atmospheric boundary layer is to be modelled, this can be selected with the wind shear type radio button. The corresponding shear parameters can then by specified (see Wind).

Uniform wind field creation dialogue in QBlade.

Fig. 88 Specification of a uniform wind field within the turbine simulation dialogue.

Hub Height File

The user has more modelling freedom when a hub-height wind file is used. This type of file can either be created manually or by using the IEC wind tool 1. This allows the specification of the velocity field at the hub height as a function of time. QBlade interpolates the time between the starting time of the file and the point where the predefined wind velocity profile (EOG in this case) should start. If the user specified simulation time exceeds the ending time in the hub-height file, QBlade will create a constant wind field with the parameters from the last entry of the hub-height file until the end of the simulation. An exemplary hubheight input file that described an extreme operating gust (EOG) at 20m/s is shown below:

Time    Wind    Horiz.  Vert.   LinH.   Vert.   LinV.   Gust
        Speed   Dir     Speed   Shear   Shear   Shear   Speed
0.000   20.000  0.000   0.000   0.000   0.200   0.000   0.000
60.000  20.000  0.000   0.000   0.000   0.200   0.000   0.000
60.100  20.000  0.000   0.000   0.000   0.200   0.000   -0.000
60.200  20.000  0.000   0.000   0.000   0.200   0.000   -0.004
60.300  20.000  0.000   0.000   0.000   0.200   0.000   -0.012
60.400  20.000  0.000   0.000   0.000   0.200   0.000   -0.028
60.500  20.000  0.000   0.000   0.000   0.200   0.000   -0.054
60.600  20.000  0.000   0.000   0.000   0.200   0.000   -0.092
60.700  20.000  0.000   0.000   0.000   0.200   0.000   -0.144
60.800  20.000  0.000   0.000   0.000   0.200   0.000   -0.209
60.900  20.000  0.000   0.000   0.000   0.200   0.000   -0.289
61.000  20.000  0.000   0.000   0.000   0.200   0.000   -0.384
61.100  20.000  0.000   0.000   0.000   0.200   0.000   -0.493
61.200  20.000  0.000   0.000   0.000   0.200   0.000   -0.614
61.300  20.000  0.000   0.000   0.000   0.200   0.000   -0.747
61.400  20.000  0.000   0.000   0.000   0.200   0.000   -0.889
61.500  20.000  0.000   0.000   0.000   0.200   0.000   -1.037
61.600  20.000  0.000   0.000   0.000   0.200   0.000   -1.188
61.700  20.000  0.000   0.000   0.000   0.200   0.000   -1.338
61.800  20.000  0.000   0.000   0.000   0.200   0.000   -1.485
61.900  20.000  0.000   0.000   0.000   0.200   0.000   -1.622
62.000  20.000  0.000   0.000   0.000   0.200   0.000   -1.748
62.100  20.000  0.000   0.000   0.000   0.200   0.000   -1.856
62.200  20.000  0.000   0.000   0.000   0.200   0.000   -1.944
62.300  20.000  0.000   0.000   0.000   0.200   0.000   -2.007
62.400  20.000  0.000   0.000   0.000   0.200   0.000   -2.041
62.500  20.000  0.000   0.000   0.000   0.200   0.000   -2.043
62.600  20.000  0.000   0.000   0.000   0.200   0.000   -2.011
62.700  20.000  0.000   0.000   0.000   0.200   0.000   -1.942
62.800  20.000  0.000   0.000   0.000   0.200   0.000   -1.834
62.900  20.000  0.000   0.000   0.000   0.200   0.000   -1.686
63.000  20.000  0.000   0.000   0.000   0.200   0.000   -1.498
63.100  20.000  0.000   0.000   0.000   0.200   0.000   -1.271
63.200  20.000  0.000   0.000   0.000   0.200   0.000   -1.005
63.300  20.000  0.000   0.000   0.000   0.200   0.000   -0.703
63.400  20.000  0.000   0.000   0.000   0.200   0.000   -0.366
63.500  20.000  0.000   0.000   0.000   0.200   0.000   0.000
63.600  20.000  0.000   0.000   0.000   0.200   0.000   0.393
63.700  20.000  0.000   0.000   0.000   0.200   0.000   0.807
63.800  20.000  0.000   0.000   0.000   0.200   0.000   1.237
63.900  20.000  0.000   0.000   0.000   0.200   0.000   1.678
64.000  20.000  0.000   0.000   0.000   0.200   0.000   2.124
64.100  20.000  0.000   0.000   0.000   0.200   0.000   2.568
64.200  20.000  0.000   0.000   0.000   0.200   0.000   3.003
64.300  20.000  0.000   0.000   0.000   0.200   0.000   3.425
64.400  20.000  0.000   0.000   0.000   0.200   0.000   3.825
64.500  20.000  0.000   0.000   0.000   0.200   0.000   4.198
64.600  20.000  0.000   0.000   0.000   0.200   0.000   4.539
64.700  20.000  0.000   0.000   0.000   0.200   0.000   4.841
64.800  20.000  0.000   0.000   0.000   0.200   0.000   5.101
64.900  20.000  0.000   0.000   0.000   0.200   0.000   5.314
65.000  20.000  0.000   0.000   0.000   0.200   0.000   5.477
65.100  20.000  0.000   0.000   0.000   0.200   0.000   5.587
65.200  20.000  0.000   0.000   0.000   0.200   0.000   5.642
65.300  20.000  0.000   0.000   0.000   0.200   0.000   5.642
65.400  20.000  0.000   0.000   0.000   0.200   0.000   5.587
65.500  20.000  0.000   0.000   0.000   0.200   0.000   5.477
65.600  20.000  0.000   0.000   0.000   0.200   0.000   5.314
65.700  20.000  0.000   0.000   0.000   0.200   0.000   5.101
65.800  20.000  0.000   0.000   0.000   0.200   0.000   4.841
65.900  20.000  0.000   0.000   0.000   0.200   0.000   4.539
66.000  20.000  0.000   0.000   0.000   0.200   0.000   4.198
66.100  20.000  0.000   0.000   0.000   0.200   0.000   3.825
66.200  20.000  0.000   0.000   0.000   0.200   0.000   3.425
66.300  20.000  0.000   0.000   0.000   0.200   0.000   3.003
66.400  20.000  0.000   0.000   0.000   0.200   0.000   2.568
66.500  20.000  0.000   0.000   0.000   0.200   0.000   2.124
66.600  20.000  0.000   0.000   0.000   0.200   0.000   1.678
66.700  20.000  0.000   0.000   0.000   0.200   0.000   1.237
66.800  20.000  0.000   0.000   0.000   0.200   0.000   0.807
66.900  20.000  0.000   0.000   0.000   0.200   0.000   0.393
67.000  20.000  0.000   0.000   0.000   0.200   0.000   0.000
67.100  20.000  0.000   0.000   0.000   0.200   0.000   -0.366
67.200  20.000  0.000   0.000   0.000   0.200   0.000   -0.703
67.300  20.000  0.000   0.000   0.000   0.200   0.000   -1.005
67.400  20.000  0.000   0.000   0.000   0.200   0.000   -1.271
67.500  20.000  0.000   0.000   0.000   0.200   0.000   -1.498
67.600  20.000  0.000   0.000   0.000   0.200   0.000   -1.686
67.700  20.000  0.000   0.000   0.000   0.200   0.000   -1.834
67.800  20.000  0.000   0.000   0.000   0.200   0.000   -1.942
67.900  20.000  0.000   0.000   0.000   0.200   0.000   -2.011
68.000  20.000  0.000   0.000   0.000   0.200   0.000   -2.043
68.100  20.000  0.000   0.000   0.000   0.200   0.000   -2.041
68.200  20.000  0.000   0.000   0.000   0.200   0.000   -2.007
68.300  20.000  0.000   0.000   0.000   0.200   0.000   -1.944
68.400  20.000  0.000   0.000   0.000   0.200   0.000   -1.856
68.500  20.000  0.000   0.000   0.000   0.200   0.000   -1.748
68.600  20.000  0.000   0.000   0.000   0.200   0.000   -1.622
68.700  20.000  0.000   0.000   0.000   0.200   0.000   -1.485
68.800  20.000  0.000   0.000   0.000   0.200   0.000   -1.338
68.900  20.000  0.000   0.000   0.000   0.200   0.000   -1.188
69.000  20.000  0.000   0.000   0.000   0.200   0.000   -1.037
69.100  20.000  0.000   0.000   0.000   0.200   0.000   -0.889
69.200  20.000  0.000   0.000   0.000   0.200   0.000   -0.747
69.300  20.000  0.000   0.000   0.000   0.200   0.000   -0.614
69.400  20.000  0.000   0.000   0.000   0.200   0.000   -0.493
69.500  20.000  0.000   0.000   0.000   0.200   0.000   -0.384
69.600  20.000  0.000   0.000   0.000   0.200   0.000   -0.289
69.700  20.000  0.000   0.000   0.000   0.200   0.000   -0.209
69.800  20.000  0.000   0.000   0.000   0.200   0.000   -0.144
69.900  20.000  0.000   0.000   0.000   0.200   0.000   -0.092
70.000  20.000  0.000   0.000   0.000   0.200   0.000   -0.054
70.100  20.000  0.000   0.000   0.000   0.200   0.000   -0.028
70.200  20.000  0.000   0.000   0.000   0.200   0.000   -0.012
70.300  20.000  0.000   0.000   0.000   0.200   0.000   -0.004
70.400  20.000  0.000   0.000   0.000   0.200   0.000   -0.000
70.500  20.000  0.000   0.000   0.000   0.200   0.000   0.000

Turbulent Wind Field

The final type of wind file which can be set up is a fully turbulent wind file. This can be either generated through the Wind Input Type button of the turbine simulation dialogue, as shown in Fig. 88 or by directly generating this within the turbulent wind module, shown in Fig. 89.

Wind field creation dialogue in QBlade.

Fig. 89 The wind field creation symbol in the QBlade main tool bar.

When a new turbulent wind file is created, a range of parameters must be specified as shown by the turbulent wind dialogue in Fig. 90. After these have been selected, clicking on the Create button automatically passes the information to the TurbSim program 2. This is linked to the QBlade release, so that no additional user input is required. The input parameters are described in detail in the following sections.

Grid Parameters

These parameters dictate the spatial dimensions of the generated turbulent wind grid. A turbulent box is be generated which is then translated through the field of interest at the average velocity (defined below) as is consistent with Taylor’s hypothesis for a turbulent flow 3.

  • Seed: The random seed used to generate the wind field.

  • Time: Determines the length of the generated turbulent box.

  • Timestep: Specifies the discretisation in free stream (\(x\)) direction.

  • Grid Width: Specifies box size in lateral (\(y\)) direction.

  • Grid Height: Specifies box size in vertical (\(z\)) direction.

  • Grid Y Points: Specifies spatial discretisation in \(y\) direction.

  • Grid Z Points: Specifies spatial discretisation in \(z\) direction.

  • Hub Height: Specifies the vertical position of the box center.

Turbine Class

These determine the turbine class as defined in the IEC 61400 design standard 4.

  • Turbine Class: Specifies the design turbine class.

  • Turbulence Class: Specifies the design turbulence class.

  • I_ref: Specifies the turbulence intensity.

  • V_ref: Specifies the reference velocity.

Flow Parameters

These parameters specify the parameters and model inputs required for generation of the turbulent velocity field.

  • Mean Wind Speed: Specifies the mean translational velocity of the frozen turbulent flow field.

  • Horizontal Inflow: Specifies the horizontal inflow angle.

  • Vertical Inflow: Specifies the vertical inflow angle.

  • IEC 61400 1-ed: Specifies the version of the IEC standard applied.

  • Wind Type: Specifies the wind class of the generated wind field.

  • Spectral Model: Specifies the form of the spectral tensor applied to generate the stochastic velocity fluctuations.

  • Wind Profile Type: Specifies the model used to represent the atmospheric shear layer.

  • Reference Height: Specifies the reference height of the aforementioned shear layer model.

  • Shear Exponent: Specifies the shear exponent of the aforementioned shear layer model (if exponential model chosen).

  • Roughness Length: Specifies the reference height of the aforementioned shear layer model (if logarithmic model chosen).

  • Jet Height: Specifies the jet height of the aforementioned shear layer model (if jet model chosen).

  • ETMC value: Specifies the extreme turbulence model \(c\) value (if ETM model chosen).

  • Remove TurbSim Files: If checked, the TurbSim files generated (and subsequently read by QBlade) is deleted.

  • Close Console: If checked, the console which is called to generate the TurbSim file is automatically closed upon completion of TurbSim file generation.

Turbulent wind field creation dialogue in QBlade.

Fig. 90 The turbulent wind field creation dialogue.

1

NREL. IECWind. https://www.nrel.gov/wind/nwtc/iecwind.html, 2022. [Online; accessed 2022-06-13].

2

B.J. Jonkman and L. Kilcher. TurbSim User’s Guide Verson 1.06.00. NREL, 2012. An optional note.

3

G.K. Batchelor. The Theory of Homogeneous Turbulence. Cambridge University Press, 1953. ISBN 0521041171.

4

IEC61400-1 Standard. IEC 61400-1:2019 Wind energy generation systems - Part 1: Design requirements. Standard, International Electrotechnical Commission, Geneva, Switzerland, 2019.