Time series wave elevation computation in HydroDyn

Dear Jason,

I’m recently reading the Hydrodyn code, but i’m not quite clear about the process from wave spectrum to the time series wave data. Could you please show me some reference or books to better understand this process?
Also, I found in the Function “JONSWAP”, there is an additional item “Inv2Pi” comparing with the formula in IEC61400-3 Annex B.3. Could you tell me why?
JONSWAP = Inv2PiC( 0.3125HsHsfpOvrf4/f )EXP( ( -1.25fpOvrf4 ) )( GAMMA**Alpha )

Best regards,

Lei

Dear Lei Liu,

In HydroDyn, the wave time series is derived from the wave spectrum through an inverse discrete Fourier transform (implemented in HydroDyn with a computationally efficient fast Fourier transform or FFT) as described in my 2009 Wind Energy journal article : www3.interscience.wiley.com/cgi- … 5/PDFSTART.

The factor of inverse 2*pi (parameter Inv2Pi) in the JONSWAP spectrum is needed to compute the spectrum with the frequencies in rad/s instead of Hz, as described in Annex B.6 of IEC 61400-3.

Best regards,

Dear Mr Jonkman,

Thank you for the reply, but i can’t access the paper now. Would you please send your paper to my email (liulei206@gmail.com)? I really appreciate that.

Best regards,

lei