Dear Jason,
I’ve set the WaveMod in HydroDyn to 5 and I’m using an externally generated irregular wave elevation time series. Despite setting the 2ND-order waves Flag to true for both mean and difference-frequencies, I’m getting linear waves in the output channel. Could you tell me what I could do to get the exact wave elevations as the data from the wave gauge?
I’m attaching a plot from gage and output channel data.
Best regards
Masih
Dear Masih,
A similar question has been asked and answered on our forum here: User input kinematics for floater in FAST - #8 by Antonio.Pegalajar. My guess is that you are applying a first-order low- and/or high-frequency cut-offs.
Please note the WaveMod = 5 option assumes that the user-specified wave elevation is first order. Adding second-order terms along with WaveMod = 5 will not allow you to get the exact wave-elevation time series back, because additional energy will be added at the difference and sum frequencies.
Best regards,
.