Wind data analysis

Articles on this page:

• Start time for turbulent wind
• Mann model for wind
• Wind data cannot be matched with the desired timeseries of wind

Problem

Regarding the “Start time for turbulent wind” there is a common misconception about this entry in Bladed.

Solution

This is not the time at which turbulent wind will begin in the simulation – this is the point within the turbulent wind file at which the turbulence is read from. So it does not allow you to delay the start of turbulent wind, but rather it allows you to start the turbulence from a different point in the file than the first point.

Keywords

Turbulence; Wind; Start

Problem

How to choose the Mann model parameters

Solution

We typically do not use the Mann model in DNV at present, but in the past the following parameters have been used:

1. Shear parameter = 3.9
2. Scale length = 33.6
3. FFT points = 128
4. Max lateral/vertical wavelength = 400m

This was for a 360m wide by 240m high wind file.

In general the advice should be:

1. Shear parameter = 3.9 – in line with the IEC edition 4 standard
2. Scale length = 33.6 = 0.8*Λ1 Λ1 is defined in IEC edition 4 standard Section 6.3.1
3. FFT points – start with 128 and increase by a factor of 2 if the reduction in turbulence due to loss of high frequency variations reported by Bladed is deemed too high (see Bladed theory manual section 10.1.4).
4. Max lateral/vertical wavelength – ensure it is at least 10% greater than the maximum of the height or width of the wind file to avoid periodicity within the wind file.

Refer to Bladed user manual section 6.10.1 and Bladed theory manual section 10.1.4. These are accessible through the help menu in the Bladed user interface.

Keywords

Mann; Aerodynamics; Wind file

Problem

Main issue: Wind data cannot be matched with the desired timeseries of wind

Source of problem: Not enough statistics is provided

Solution

Matching wind data to a desired time series is essential for accurate energy modelling. A key challenge in this process is using a wind data file that's too short, which leads to poor statistics and unreliable results.

Key points:

1. Extend Wind Data Duration:
   • The wind data file must be long enough to provide accurate statistics.
   • Extend the wind data duration to improve the accuracy of the time series match.
2. Data Length for Time Series Matching:
   • The wind data set from wind field test for matching should be longer than the target time series.
   • To achieve a longer data set, consider mirroring the existing data.

Keywords

Wind data; wnd file