Turbsim EWM 1hour wind time series (IEC 61400-3 DLC6.1)

[EWEMkite]

Dear @jjonkman ,

I am now using Turbsim to generate the EWM wind time series of 5400s for simulation of IEC 61400-3 DLC6.1.

Knowing that EWM is only valid for maximum 10min setting of AnalysisTime setting, refer to post:[https://forums.nrel.gov/t/turbsim-how-to-run-60-minutes-simulations-with-repeating-10-min-turbsim-output-files/4684/6], is it suitable to generate repeated wind time series for DLC6.1 simulation? I am not sure if this is stated in the IEC 61400-3 standard. I read some other posts, which suggest to run 6 seprate simulations with different seeds for this case to extend simulation time from 10min to 1hour, but won't there be discontinuity problem between each? I want to know what approach is mostly suggested for this case (IEC 61400-3 DLC6.1).

I also see a tool called IECwind which is potentially better for this, but I can't open the download link on NREL, is it being maintained now? Or could you please give me a link for download?

Best Regards,
Zekai Tao.
Turbsim.txt

[jjonkman]

Dear @EWEMkite,

DLC 6.1 in IEC 61400-3 (or IEC 6140-3-1 for fixed-bottom and IEC 61400-3-2 for floating wind turbines) is typically run with 6 seeds of 1-hour simulations, but the IEC also permits 6 groups of 6 10-minute simulations. See clause 7.5.6 for details. When using 1-hour simulations, you should reduce the 10-minute reference wind speed and increase the 10-minute reference turbulence, which is also explained in the standard, i.e., Vhub_1hr = Vhub_10min * 0.95 and sigma_1hr = sigma_10min+0.2 m/s. See clause 6.4.3 for details. The standard does not recommend using 10 minute winds that are periodic and repeat over 1 hour, because this would imply that the 10-minute extreme wind condition persists longer than 10 minutes.

I agree that selecting one of the "EWM" models for IEC_WindType in TurbSim are only valid for 10-minute simulations. To get around this limitation of TurbSim, e.g., to run 1-hour simulations, you can select ("NTM") and specify your own turbulent standard deviation in IECturbc and wind speed in URef to match the IEC recommended values.

Best regards,