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 helpand here I also attach my .dat and .cif files that I used.Spar.datSpar.dat
thanks for the help
Hi Gilrandi,
The message I saw was "Warning: Block SPAR is Being Redefined". This was in the output file. There may be a reason why a block is being redefined. That is why the message is labeled as a warning.However, in your analysis there was not need to read the model in twice. That is why I reported it to you as an error.
It looks like you now need to tune the results.
Cheers,
Georgina Maldonado
Hello Georgina,I revised my cif and dat file according to your review, and I got a better result now. I got 0.061 damping coefficient in encounter period 23s using the new set of dat and cif file. which is equal to 2132.854 KN/(m/s).Yet, I didn't see any difference in the result between cif file with "-auxin" option and without one. Can you explain to me why it becomes an error when I use "-auxin" option?Thank you for your help.
First there is an error in the command file. Line 09 should not have the "-auxin" option. The model is being read in twice.
You know you can run the file for only period 23, while you are testing things out.
Try running it again with only period 23 and let me know what value you get.
Georgina
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
Can you tell me exactly what number you are comparing? Please send back a message similar to the following.
Please see output file page X and line number Y. I am looking at column N.
georgina