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**Sinisa Knezevic****Member**- From: Zagreb, Croatia
- Registered: 2010-01-12
- Posts: 9
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Dear,

I am interested in clearing out this issue of turbulence structure.

First, I presume it is the ratio of turbulences from all directions (in m/s). Correct me if I'm wrong.

Second - is there a way to calculate it in WEng 3.1?

Thank you!

Regards,

Sinisa

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Dear Sinisa,

IEC 61400-12-1 on power performance measurements has an informative Annex M discussing how to correct a measured power curve for effects of turbulence. However, it does not depend on ratios of standard deviations of turbulent fluctuations in different directions (sigmaU, sigmaV and sigmaW). I am therefore guessing that your actually ask about the turbulence structure correction parameter CCT, which is specified in IEC 61400-1 on turbine safety. Actually you can calculate this in two alternative ways – by terrain assessment or by a formula based on sigma-ratios. You can make either assessment with our WAT program, which is a postprocessor of results from WAsP and WEng. WAT calculates CCT by probability-weighted averages of standard deviations of turbulence components in a number of sectors as calculated by WEng. The data for WAT is calculated by a tool called ‘Prepare data for WAT’ inside WEng 4. Learn more in videos no. 2, 3 and 6 at https://www.youtube.com/playlist?list=P … qJ5UXlHvYA

I am not sure, but I think the preparation of data for WAT worked the same way with WEng 3.1 If not, you may have to upgrade or make equivalent assessments manually using the turbulence calculated for a number of wind directions inside WEng.

With best regards,

Morten Nielsen

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**Sinisa Knezevic****Member**- From: Zagreb, Croatia
- Registered: 2010-01-12
- Posts: 9
- Website

Dear,

Sorry I wasn't explicit enough... I was actually asking about anemometer classes according to IEC 61400-12-1 Ed.2 (Annex I, Table I.1) in which anemometer class depends on turbulence structure.

Thank you once more!

Regards,

Sinisa

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