Dear @Yangyang.Li,
My interpretion of IEC 61400-1 Ed. 4, which matches what is done in TurbSim, is that the NTM represents the turbulence defined in (10) that is superimposed on the NWP defined (9). So, TurbSim should be consistent with IEC.
Best regards,
Dear @Jason.Jonkman ,
When the parameter IECstandard = 3 is specified in the primary input file of the wind field generator module (inp), the turbulence standard deviation generated by TurbSim for offshore wind turbines will be increased by 0.2 m/s on the basis of the onshore value, according to Equation (9) of IEC 61400-3-1 (Edition 1.0, 2019).
For the specific wind condition models listed below, the onshore baseline values are calculated from Equation (10) for NTM, Equation (17) for EWM, and Equation (20) for ETM , where both the equation numbers and the terminology of the wind condition models are taken from IEC 61400-1 (Edition 4.0, 2019). If any understanding here is incorrect, please kindly point it out. TurbSim is from OpenFAST-v4.1.2.
Best regards,
Dear @Yangyang.Li,
I agree with your summary regarding TurbSim’s treatment of NTM, EWM, and ETM matching the specifications of IEC 16400-1 Edition 4.0, 2019.
However, TurbSim does not include Equation (9) of IEC 61400-3-1 Edition 1.0, 2019, which is used to increase the turbulence standard deviation when switching from a 10-min to a 1-hour averaging period. If you wish to simulate 1-hour simulations based in Equation (9), you should define your own turbulence intensity through IECturbc in TurbSim.
Best regards,