Damping of SPAR floating structure using heave plate

Hi all, I really need some help with my undergraduate thesis. So, I've been analyzing the effects of heave plate in the keel of SPAR to motion response of the SPAR structure using MOSES, and experimental trials. so here is my question.

As far as I know, MOSES generates 6x6 full matrices damping and added mass in .ppo file that has 1/time unit for translational and m^2/s for rotational in its damping matrices. I've been using this to validate my experimental analysis result. from my decay tests in my experimental analysis, the value of B33 (heave damping) of my SPAR using heave plate is approximately 1536 KN/(m/s). But, from my MOSES analysis, I only got 241.626 KN/(m/s) for B33 (heave damping), I got this result from B33 component in the matrix damping times displacement of my SPAR (because the unit of .ppo matrix is the result from damping/mass). In my .dat file, I'm using -cs_current 1 1 1 command to calculate the damping of my SPAR. Am I using the wrong command? As before I used -tanaka and the result is lower.

thanks for the help

and here I also attach my .dat and .cif files that I used.

Spar.datSpar.dat

thanks for the help

Parents Reply
  • Of course,

    Please see output file page 39 (linearized damping coefficient section), line number 49 (encounter period 23 s). I am looking at column heave (the value is 0.1108).

    I chose to compare encounter period 23s because of my model, in a free-floating state (that has draft 129.305 m) has approximately 23s heave natural period. But in my cif file, I'm using the moored state (that has draft 139.365 m), because I use moored condition in decay test of the model.

    and I only pick one encounter period because I also use this result in Orcaflex to analyzed the moorings parameters, which requires damping and added mass matrix in one encounter period as an input that corresponds with the structure. And the result is very unsuitable with my experiment result. I believe this is because of the damping that I used doesn't match with the model tests. Can I also ask your professional opinion about these?

    Thank you

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