# Second-order waves

**URL:** <https://forums.nlr.gov/t/second-order-waves/1768>\
**Category:** Computer-Aided Engineering Software Tools\
**Created:** [January 15, 2018, 8:38pm UTC](https://forums.nlr.gov/t/second-order-waves/1768 "2018-01-15T20:38:15Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![Jason.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/jason.jonkman/32/3086_2.png) [@Jason.Jonkman](https://forums.nlr.gov/u/Jason.Jonkman)\
**Post date:** [January 16, 2018, 7:53am UTC](https://forums.nlr.gov/t/second-order-waves/1768/2 "2018-01-16T07:53:31Z")

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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](http://forums.nlr.gov/t/user-input-kinematics-for-floater-in-fast/1472/8). 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,

.

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