Wind Field Batch

The Wind Field Batch panel generates a structured set of TurbSim wind fields by sweeping across multiple parameter axes simultaneously. It is the primary way to build the wind input matrix for fatigue load analyses and design load calculations (DLCs). Click Wind Field Batch under BATCH in the sidebar to open it.

Overview

The panel is divided into three sections: turbine parameters (auto-populated from the active model), sweep parameters (user-defined axes), and grid/execution configuration.

The right side shows a live preview of the wind field for the most recently completed case.

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Sweep modes

Two sweep strategies are available via the Factorial and Paired buttons at the top of the sweep parameters section.

Mode	Behaviour
Factorial	Every combination of every axis value is generated. 11 wind speeds × 2 TI values × 3 shear values × 2 gTI values = 132 cases per seed
Paired	Axis values are stepped together in lockstep. All axes must have the same number of values. 5-element axes → 5 cases per seed

Factorial mode is appropriate for full design load studies. Paired mode is useful when axis values have a physical relationship — for example, sweeping matched (wind speed, shear exponent) pairs extracted from site measurements.

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Sweep parameters

Wind speeds

A comma-separated list of mean hub-height wind speeds in m/s. For IEC NTM fatigue analyses, the standard range is 4–24 m/s in 2 m/s steps:

4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24

Wind type

Selects one or more IEC wind condition types to include in the sweep:

Type	Description
NTM	Normal Turbulence Model — standard fatigue loads
NETM	Not-extreme Turbulence Model
EWM1	Extreme Wind Model, 1-year return period
EWM50	Extreme Wind Model, 50-year return period

Multiple types can be selected simultaneously; each becomes an additional axis in the factorial sweep.

TIs (ref)

Reference turbulence intensity values in percent. These override the IEC class-derived TI and allow custom turbulence levels to be swept directly:

4, 8, 12, 16

Wind class

Selects IEC turbulence classes (A, B, C) as an alternative to explicit TI values. When wind class is active, the reference TI for each class is derived from the IEC 61400-1 formula at each wind speed. Wind class and explicit TI axes are mutually exclusive — activating wind class overrides the TI field.

Shear exponent (α)

Power-law wind shear exponent values to sweep. A value of 0.2 is the IEC standard for normal wind conditions onshore; 0.1 is typical offshore:

0.1, 0.2, 0.3

TI asymmetry (gTI)

Turbulence intensity gradient across the rotor disk (see Gradient Turbulence Intensity). A value of 1.0 gives a uniform profile (standard IEC). Values above 1.0 apply an increasing gradient from rotor top to bottom.

1.0, 1.15, 1.2

Note

Cases with gTI > 1.0 automatically switch the wind profile type from a standard power-law profile to a USR (user-defined) wind profile. This is handled internally — no manual configuration is needed.

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IEC configuration

Setting	Description
Turbulence model	Spectral model: IECKAI (Kaimal, recommended) or IECVKM (von Kármán)
Seeds per condition	Number of statistically independent realisations generated for each unique parameter combination. A minimum of 6 seeds is required by IEC 61400-1 for fatigue analyses

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Wind field grid

Setting	Description
Grid points (Z × Y)	Vertical × lateral grid resolution. Default 15×15
Grid size (W × H)	Physical dimensions of the grid in metres. Should cover at least the full rotor swept area
Usable time	Duration of wind data written to the .bts file (the portion OpenFAST reads)
Analysis time	Total TurbSim simulation time, always slightly longer than usable time to avoid edge effects

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Parallelism

The Parallel TurbSim workers selector controls how many TurbSim processes run simultaneously. FlowUrja Studio detects the number of logical CPU cores and recommends leaving one core free for system tasks. For a 4-core machine, 3 parallel workers is the default.

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Batch label and output path

The Batch label is a short identifier for the sweep run (e.g. NREL_15_MW_study1). It appears in the output directory path:

wind/sweeps/{batch_label}_{YYYYMMDD}_{HHMMSS}/

A timestamp is appended automatically so repeated runs with the same label never overwrite each other.

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Case count and naming

The panel shows a live case count summary as you configure the sweep:

2 speeds × 1 type × 2 TIs × 2 shear × 1 seeds = 16 cases

Each generated case file follows a systematic naming convention encoding all parameters:

Custom_IECKAI_TI004_NTM_V04ms_149m_15x15_PLX010_gTI115_s01.bts
         │      │     │    │     │    │     │       │      └─ seed index
         │      │     │    │     │    │     │       └──────── gTI (omitted when 1.0)
         │      │     │    │     │    │     └──────────────── shear exponent ×100
         │      │     │    │     │    └────────────────────── grid (NZ×NY)
         │      │     │    │     └─────────────────────────── hub height
         │      │     │    └───────────────────────────────── wind speed
         │      │     └────────────────────────────────────── wind type
         │      └──────────────────────────────────────────── reference TI ×100
         └─────────────────────────────────────────────────── spectral model

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Running the batch

Click Generate .inp files to write all TurbSim input files without running them — useful for inspecting or archiving the input matrix. Click Stop (which replaces the run button when the batch is active) to halt at any point; completed cases are preserved.

During the run, completed cases appear in a scrolling list with green checkmarks. The batch can be stopped and resumed; already-completed cases are skipped on restart.

When all cases complete, the output directory is ready to be imported into the Simulation Batch panel.