Value of WaveTp in OpenFast

Hello everyone,

The IEC 61400-3-1:2019 says that the wave period T can range from 11.1*sqrt(H_s / g) to 14.3*sqrt(H_s/g). However, OpenFast requires Peak spectral period, WaveTp for WaveMod=2 (JONSWAP/Pierson-Moskowitz spectrum).

Is the above range applicable to WaveTp? That is,

11.1 * sqrt(H_s / g) ≤ WaveTp ≤ 14.3 * sqrt(H_s/g).

Or, I noticed that the peak spectral period T_p≈1.2T_0 for the JONSWAP spectrum, in which T_0 is the mean wave period. Is the notation T in IEC 61400-3-1 Eq. (10) equivalent to T_1, and I should use the range

1.2 * 11.1 * sqrt(H_s / g) ≤ WaveTp ≤ 1.2 * 14.3 * sqrt(H_s/g)

Thanks for your help.

Best regards,
Xingchao Wang

Dear @Xingchao.Wang,

The equation you are referring to from IEC 61400-3-1:2019 applies only to the range of wave periods associated with the extreme individual wave height in deep water when the site-specific metocean data is insufficient to determine it. This equation does not apply to normal wave conditions or irregular sea states. This equation could be used to determine the range of wave periods associated with extreme individual wave heights to be applied via constrained NewWave theory when simulating load cases involving Extreme Sea States (ESS). Constrained NewWave theory has been added to the new SeaState module of OpenFAST that will be first released in OpenFAST v4.0:

Best regards,

Dear @Jason.Jonkman,

Thank you for your detailed answer. I will refer to books on the topic of random waves.

Best regards,
Xingchao Wang