MOSES - During Motion analysis study of a vessel, the linearization of Added mass & Damping coefficient is done by 1/20 & is apparently divided by weight of the vessel. Do we have any separate reference for the above process in MOSES Manual in detail. Technically what is the reason for doing this ? Is it a generalized process ?
Hi Siddarth,
Thank you for your continued interest in our offshore products.
The linearization of added mass and damping coefficient is reported as a normalized value. The normalized value is what you are seeing in the added mass and damping reports. When the program does the computations it uses the in-normalized.
Yes, the default for computing RAOs is to us a 1/20 wave steepness is used to linearize the equations spectrally. In the equations you have to put something for the forcing function. Here is the link to the wiki page.
https://en.wikipedia.org/wiki/Response_amplitude_operator
In the past (1970s) we could not afford the computer time to linearize based on a wave spectrum. Today, there is the option "-spectrum" if you want to linearize based on a wave spectrum
I hope the above helps.
Georgina Maldonado
Answer Verified By: Siddharth Manda
Hi Georgina,
I hope you are well.
I'm sticking to this discussion for clarification. I normally use the 1/20 linearization for deep water; is there any issue in using 1/20 for shallow water? If yes, what linearization do you advise?
Thanks
Pietro
Hi Pietro,
It is nice to hear from you. Happy New Year!
I have to admit I have limited experience in shallow water. From my experience I have not seen much difference in using spectral linearization and the 1/20 linearization. What I have seen makes a difference is using an obstacle to model the sea floor.
We are planning an enhancement to the hydrodynamic computations to address the shallow water problem.
Please stay tuned.
Thank you,
Thanks for your prompt reply and happy new year to you!
When you say "What I have seen makes a difference is using an obstacle to model the sea floor" do you assume that no problem will come using ¶meter ?
for example
&PARAMETER -DEPTH 7.5